U.S. Highway 131
US 131 highlighted in red
Route information
Auxiliary route of US 31
Maintained by INDOT and MDOT
Length	266.82 mi[note 1] (429.41 km)
Existed	November 11, 1926[1]–present
Major junctions
South end	I-80 / I-90 / Indiana Toll Road / SR 13 near Middlebury, IN
Major intersections	I-94 near Kalamazoo, MI M-6 in Wyoming, MI I-196 in Grand Rapids, MI I-96 in Walker, MI US 10 near Reed City, MI M-55 at Cadillac, MI M-66 / M-72 at Kalkaska, MI
North end	US 31 at Petoskey, MI
Location
Country	United States
States	Indiana, Michigan
Counties	IN: Elkhart MI: St. Joseph, Kalamazoo, Allegan, Kent, Montcalm, Mecosta, Osceola, Wexford, Grand Traverse, Kalkaska, Antrim, Charlevoix, Emmet
Highway system
United States Numbered Highway System List Special Divided
← SR 130 IN → SR 134 ← M-130 MI → M-131

U.S. Highway 131 (US 131) is a north–south United States Highway; all but 0.67 miles (1.08 km) of its 266.82 miles (429.41 km) are within the U.S. state of Michigan. The highway starts in rural Indiana south of the state line as a state road connection to the Indiana Toll Road. As the road crosses into Michigan, it becomes a state trunkline highway that connects to the metropolitan areas of Kalamazoo and Grand Rapids and north to its terminus at Petoskey. US 131 runs as a freeway from south of Portage north to Manton. It forms an important corridor along the western side of the Lower Peninsula of Michigan, running through rural farm and forest lands as well as urban cityscapes.

The first state highways along the US 131 corridor were designated by 1919. Later when the US Highway System was formed on November 11, 1926, US 131 was created along the route of M-13 in Michigan, but it did not extend south into Indiana at the time, ending at the state line. Originally ending at Fife Lake on the north end, the highway was extended to Petoskey in the late 1930s. Further changes were made starting in the 1950s to convert segments of the road to a full freeway. The state started near Three Rivers and went north while simultaneously extending both north and south from a point in southern Kent County. A third segment was built south of Cadillac and over the subsequent years, Michigan filled in the freeway gaps. Cadillac and Manton were bypassed in the early part of the 21st century, resulting in the current freeway configuration. Another large-scale construction project rebuilt an unusual section of the freeway through Grand Rapids known as the S-Curve in 2000.

Future plans to extend the freeway further have either been cancelled, or been placed back under study. Upgrades on the north end through Kalkaska are not being considered at this time. South of Three Rivers, the Michigan Department of Transportation (MDOT) is studying future upgrades to US 131. One option for these upgrades is a full freeway, an option that was initially rejected. The current preferred alternative is a two-lane bypass of Constantine.

Running 266.82 miles (429.41 km) in Indiana and Michigan, the full length of US 131 is listed as a part of the National Highway System,^[2][3] a system of roads important to the nation's economy, defense and mobility.^[4] As a state highway in both states, the roadway is maintained by the Indiana Department of Transportation (INDOT) and the Michigan Department of Transportation (MDOT). The Michigan section includes approximately 172 miles (277 km) of freeway between Kalamazoo and Wexford counties.^[5]

US 131 extends 0.67 miles (1,078 m) through Elkhart County, Indiana between the entrance to the Indiana Toll Road, a few hundred feet north of the Toll Road overpass and the state line to the north. State Road 13 (SR 13) runs concurrently with US 131 in this section but is not signposted.^[6][7] INDOT surveys the roads under its control on a regular basis to measure the amount of traffic using the state's highways. These traffic counts are expressed in terms of annual average daily traffic (AADT), which is a calculation of the number of vehicles on a segment of roadway for any average day of the year. In 2007, INDOT determined that 7,949 cars and 2,068 trucks used the section of US 131 daily in the state of Indiana.^[8]

US 131 runs for a distance of approximately 266 miles (428 km) in Michigan, from the Indiana state line northerly to Petoskey.^[5] The highway is an important link between Grand Rapids and the tourist areas of Northern Michigan.^[9] The trunkline enters Michigan about three miles (4.8 km) south of White Pigeon, crossing a branch of the Michigan Southern Railroad before meeting US 12 on the west side of the village.^[10] The highway runs through rural farmland north to Constantine, where US 131 turns northeasterly through a residential area of town. Passing through the downtown business district, US 131 crosses the St. Joseph River and turns to run along the west bank of the waterway north to Three Rivers.^[11][12] The one of the lowest AADT counts for Michigan was measured along the stretch of highway between Constantine and the start of the divided highway south of Three Rivers. This roadway segment averaged 7,579 cars and 1,045 trucks daily in 2009 according to MDOT.^[13]

US 131 runs through a business corridor along the west side of Three Rivers. M-60 runs concurrently along this part of US 131 until the two highways meet the south end of the business loop through town. M-60 turns east to follow Business US 131 (BUS US 131) into downtown and the main road curves to the northeast out of town.^[11][12] The trunkline runs parallel to a branch of the Grand Elk Railroad.^[10] North of the other end of the business loop, US 131 follows a four-lane expressway-style highway through rural farmland in northern St. Joseph County. The highway has at-grade junctions with cross roads and intermittent driveways, but otherwise is designed like a freeway with limited access from adjoining property.^[12] This arrangement ends on the south side of Schoolcraft where the highway transitions to follow Grand Street through town. North of town, US 131 returns to an expressway again as the highway continues through southern Kalamazoo County farmland.^[11][12]

After the intersection with Shaver Road, US 131 widens into a full freeway. This freeway passes the Gourdneck State Game Area as it enters the Kalamazoo metropolitan area. US 131 meets I-94 southwest of Kalamazoo and picks up the Business Loop I-94 (BL I-94) designation for a couple miles. This secondary designation leaves the freeway at exit 36 and follows US 131's business loop along Stadium Drive into downtown Kalamazoo near the main campus of Western Michigan University. As the freeway passes the west side of Kalamazoo, the surrounding environs change to a more forested and semi-residential area. US 131 passes the northern end of BUS US 131, which is a freeway spur accessible from the southbound direction of US 131. North of this partial interchange, the freeway crosses into eastern Allegan County.^[11][12]

As US 131 passes through the outskirts of Plainwell, the freeway curves to the northeast through a commercial area centered around the interchange with M-89. North of this area, US 131 crosses the Kalamazoo River and runs past the US 131 Raceway Park, a dragstrip near the M-222 interchange near Martin. The freeway continues north through mixed farm and forest lands to the residential areas that abut it in Wayland. Further north, the highway crosses into Kent County and the southern end of the Grand Rapids metropolitan area.^[11][12]

As the freeway continues farther north and closer to Grand Rapids, it is lined with more commercial and light industrial properties.^[12] The unincorporated suburb of Cutlerville lies to the east as US 131 approaches the "mammoth" interchange with M-6, the South Beltline Freeway, that stretches over a half mile (0.8 km) in width and over a mile (1.6 km) in length,^{[note 2]} encompassing 27 bridges and 18 retaining walls; this makes it the largest freeway interchange in West Michigan.^[14] US 131 continues north through the city of Wyoming to the more suburban residential areas near the southern city limits of Grand Rapids north of M-11 (28th Street).^[11][12]

The southern end of Grand Rapids continues with residential areas along US 131 until Burton Street, where a large rail yard abuts the trunkline on the east the freeway turns northeasterly on its approach to downtown. At Wealthy Street, the freeway takes a sharp turn to the west to cross the Grand River and immediate turns back north on a bridge structure known as the S-Curve.^[11][12] North of this river crossing, US 131 experiences its most traffic. In 2009, MDOT measured an AADT of 107,200 cars and 5,992 trucks through the stretch between Market Avenue and Pearl Street.^[13] The trunkline continues past the Gerald R. Ford Museum and the Public Museum of Grand Rapids before the two carriageways that form the freeway cross each other. The northbound carriageway crosses over the southbound lanes meaning that traffic through this stretch briefly drives on the left. On the other side of this interchange, the northbound carriageway crosses back under the southbound lanes, restoring the standard driving configuration.^[15] North of I-196, US 131 picks up a second, hidden designation. The section of freeway is also called I-296 on highway inventory logs,^[16] although the number is not signed along the road.^[11][15] I-296/US 131 continues along the banks of the Grand River into Walker where the hidden I-296 designation turns to the northwest along a series of ramps to I-96 while US 131 curves to the northeast along a bend in the river.^[5] As it continues along the river, the freeway passes through the unincorporated community of Comstock Park and near Fifth Third Ballpark, which is home of the West Michigan Whitecaps, the local minor league baseball team.^[12]

The trunkline turns north and away from the river near the stadium as it passes through the remainder of the northern suburb, changing to a more rural character as the freeway passes through the northern end of Kent County. M-46 joins US 131 from the west at Cedar Springs, and the two highways pass into northwestern Montcalm County near Sand Lake. North of Pierson, the landscape is dominated by forests. M-46 turns east and leaves the freeway near Howard City, and US 131 continues into Mecosta County near the Little Muskegon River.^[11][12] The freeway forms the eastern boundary of the Manistee National Forest near the river and north to Big Rapids.^[17] Further north, M-20 joins the US 131 freeway near Stanwood, and the two highways cross the Muskegon River on the way to Big Rapids. The city is served by its own business loop and M-20 turns east off the freeway along BUS US 131 toward the main campus of Ferris State University. North of Big Rapids, US 131 runs through rural Osceola County to a junction with US 10 at Reed City.^[11][12]

Passing through rural Osceola County and providing access to rural communities like Leroy and Tustin, US 131 approaches the south side of Cadillac in Wexford County. At exit 176, M-55 leaves a concurrency with M-115 and joins the US 131 freeway around the east side of Cadillac. This bypass was built in the early 21st century, and the old routing is now a business loop through downtown. M-55 follows the freeway to exit 180, and US 131 continues around the east side of Cadillac and north around the east side of Manton. On the northeast side of the latter community, US 131 has the lowest freeway traffic counts as it transitions back to a two-lane, undivided highway before meeting the north end of Manton's business loop.^[11][12] Through this area, only 7,455 cars and 709 trucks used the northernmost part of the freeway daily in 2009.^[13]

The two-lane highway runs through through the Pere Marquette State Forest and over the Manistee River,^[12] crossing through the southeast corner of Grand Traverse County. The highway meets the southern end of M-113 in Walton,^[11] and it runs parallel to the Great Lakes Central Railroad.^[10] Passing through Fife Lake, US 131 crosses into Kalkaska County and to South Boardman. The area around South Boardman is marked by farmland as the trunkline crosses the Boardman River in the small unincorporated community. The road once again runs parallel to the railroad as it meets M-66/M-72 south of Kalkaska. The three highways join together and run concurrently through downtown. North of town, M-72 turns west toward Traverse City, and US 131/M-66 continues north through farmland into Antrim County.^[11][12] About 3–3.5 miles (4.8–5.6 km) north of town, standing on the west side of the road is the Shoe Tree. A local landmark since shortly after the turn of the 21st century, the origins of the artwork are unknown, but the owners of the property call it "the best landmark in Northern Michigan".^[18]

The trunkline follows the railroad into Antrim and Mancelona. North of downtown Mancelona, M-66 turns north toward Charlevoix, and US 131 continues along the Mackinaw Trail through Alba. M-32 follows US 131 for a half mile (0.8 km) near the community of Elmira. As it continues farther north, US 131 enters the Mackinaw State Forest.^[11][12] This section of roadway is where MDOT measured the lowest traffic counts of all on US 131. In 2009, 5,114 cars and 448 trucks traveled the road daily.^[13] The highway passes through rural Charlevoix County. The terrain through this area has many rolling hills as the road descends down to the elevation of Lake Michigan. As the highway enters the southern section of the city of Petoskey, it runs along Spring Street and passes retail establishments and the Odawa Casino, owned by the Little Traverse Bay Indian Reservation of Odawa Indians. The northern terminus of US 131 is at the intersection of Spring Street and Charlevoix Avenue. US 31 turns off Charlevoix Avenue and follows Spring Street north of US 131.^[11][12]

MDOT operates 67 rest areas and 14 welcome centers in the state named in honor of retired department employees.^[19] There are eight rest areas along US 131 that provide locations for motorists to pull off the highway. These areas provide bathroom facilities, dog runs, picnic areas and usually vending machines.^[20] Those along the freeway serve only one direction of traffic, while the others are accessible from both directions. The rest areas near Kalamazoo, Rockford, Big Rapids and Tustin serve southbound traffic, while those near Morley and Cadillac serve the northbound side of the freeway. The two near Manton and Fife Lake are accessible from both travel directions.^[11] A ninth rest area previously existed near Cutlerville on the northbound side of US 131.^[20] This location was torn down on January 22, 2001 to make way for the interchange with M-6. The department had plans to build a replacement near Dorr, but they were cancelled in in late 2001.^[21]

MDOT removed the honoree's name from the Tustin rest area in early 2011. The former employee, Larry Brown, was a district engineer that retired from the department in 1997 after 30 years of service. He pleaded no contest on a sexual assault charge, prompting MDOT to remove his name from the rest area when notified of of his conviction. A new honoree will be chosen by the department's Rest Area Committee.^[19]

In addition to the rest areas, MDOT has built car pool lots for motorists along the freeway. There are 21 lots provided in total; all but one are located adjacent to a freeway interchange.^[11] These lots are part of a car pooling system that the department touts as a way to save money and benefit the environment.^[22] To support the lots, MDOT has partnered with a network of local agencies to offer Local Rideshare Offices that support the program.^[23]

The first highway along the path of US 131 was M-13, a designation applied to the road by July 1, 1919.^[24] US 131 debuted, along with the rest of the U.S. Highway System, on November 11, 1926, although at the time it only ran from the Michigan–Indiana state line northerly to the small Northern Michigan community of Acme in Grand Traverse County.^[25] The highway's northern section was not designated in the field, and the designation ended instead at Fife Lake. At the same time, the Michigan State Highway Department (MSHD) redesignated the remainder of M-13 between Fife Lake and Petoskey as M-131.^[26] In 1931, Public Act 131 allowed the MSHD to take control over the city streets that carried state highways through cities in the state.^[27] The department took control and fixed the routing of US 131 through the city of Grand Rapids after the act's passage.^[28] The highway was shifted between Three Rivers and Constantine to the west side of the St. Joseph River in 1936.^[29][30] In late 1938 or early 1939, the MSHD extended US 131 northward over the southern section of M-131. After the change, US 131 turned east into Fife Lake and north to Kalkaska and Mancelona before ending in Petoskey. This extension connected US 131 directly to its parent highway, US 31, for the first time.^[31]

In 1940, a new roadway was opened completing the third side of a triangle between the junction with M-113, Walton Corners and Fife Lake. US 131 was shifted to it and the former routing along the other two sides of the triangle became part of M-113 and M-186.^[32] A second realignment opened the following year between Fife Lake and Kalkaska. US 131 no longer turned east along Boardman Road between South Boardman and Lodi. Instead the highway ran directly to the northeast from the end of the previous new routing north of Fife Lake to Kalaska.^[33] By 1945, a Bypass US 131 was created around the south and east sides of Grand Rapids following 28th Street and East Beltline Avenue. The main highway continued to run through downtown, unchanged.^[34] A decade later, mainline US 131 was rerouted around Grand Rapids over the former bypass route, and Business US 131 (BUS US 131) was created for the former route through downtown.^[35][36] A second business loop was created in Three Rivers, Michigan after an expressway bypass of that city's downtown was opened in early 1954.^[37]

Another expressway section was opened between Mancelona and the M-32 junction west of Elmira in late 1956 or early 1957.^[38][39] By the end of 1957, US 131 was extended north of the Three Rivers bypass as a full freeway to Moorepark and the section of freeway in the Grand Rapids area opened near the southern county line north to 28th Street.^[40] This latter freeway segment was extended further south to Wayland by the middle of 1958.^[41] By the middle of 1960, the freeway was extended to M-118 in Martin where traffic used M-118 to connect back to the old routing. The southern end of US 131 was moved to another location on the state line. Instead of running concurrently with US 112 between White Pigeon and Mottville, US 131 ran directly south of With Pigeon to the state line. In the process the M-103 designation was swapped with US 131.^[42] The expressway section near Mancelona was reverted back to its previous state in 1961 when one of the carriageways was removed.^[43] Another project through the end of 1961 extended the freeway farther south to Plainwell and farther north into downtown Grand Rapids. This latter extension was designated as part of BUS US 131.^[44] and opened in December 1961. The opening ceremony for the bridge across the Grand River included the state highway commission and the then-current Miss Michigan pulled by a team of sled dogs to lead the first traffic over the river.^[45]

Until the early 1960s, US 131 never left the state of Michigan; the southernmost point was always at the Indiana state line. In 1961, the highway designation was extended to its current southern terminus in rural Elkhart County at a connection with the Indiana Toll Road at the request of the state of Michigan. The MSHD asked the Indiana State Highway Department (ISHD) to extend US 131 farther to reconnect with US 31 in Indiana near Indianapolis. Officials with the IHSD were said to be "receptive to the idea" by Michigan State Highway Commissioner John C. Mackie.^[46]

On December 17, 1962, the freeway through downtown Grand Rapids, including the section marked as I-296 was completed.^[47] The business loop was removed from the section of freeway opened in 1961 when US 131 was moved to the freeway. East Beltline Avenue is renumbered as an extension of M-44, 28th Street retains the M-11/M-21 designations it had in addition to US 131. I-296/US 131 runs along side the Grand River between I-96 downtown and I-196 north of town.^{[note 3]} At the end of I-296, US 131 followed I-196 east to the northern portion of the business loop at Plainfield Avenue, and followed Plainfield Avenue back to the remainder of its routing north of Grand Rapids.^[47] The other end of the freeway was extended south to M-43 on the west side of Kalamazoo. Traffic there is directed along M-43 into downtown to connect with the remainder of the highway.^[49]

Freeway construction continued through the 1960s. By the end of 1963, the southern section of freeway was extended to Schoolcraft.^[50] The following year, a business loop in Kalamazoo was created. The new loop used a freeway stub on the north and M-43 on the south to connect the main highway into the former routing of US 131 along Westnedge and Park avenues downtown.^[51] A discontinuous segment of freeway south of Cadillac into Osceola County opened in September 1966.^[52] The freeway was extended north from the Grand Rapids area to M-57 (14 Mile Road) near Cedar Springs in 1969.^[53]

The 1970s saw the US 131 freeway expand to the north of Grand Rapids. The section between the two M-57 junctions near Rockford and in Cedar Springs opened on September 21, 1973 at a dedication ceremony featuring then Congressman Gerald R. Ford.^[54] By the end of the year, the freeway would be open as far north as Howard City. At the same time, M-46 was realigned to extend south down the freeway to Cedar Springs and west to replace M-57 west of Rockford.^[55]

Construction to complete these sections north of Grand Rapids had been delayed in 1967. Before the delays, the MSHD planned to have the gap in the freeway between Grand Rapids and Cadillac completed by 1974.^[56] The state even proposed adding the freeway north of Grand Rapids to Petoskey with a further continuation to Mackinaw City as part of the Interstate Highway System in an effort to get additional funding.^[57]

The 12.2-mile (19.6 km) section of US 131 freeway south of the Wexford–Osceola county line was opened on November 9, 1976 at a cost of $7.4 million.^[58] By 1977, the state postponed any plans to complete the freeway north of Cadillac. The department cited rising construction material costs and opposition to the freeway in Petoskey.^[59] By the end of the decade, the I-296 signs were removed from that section of freeway in Grand Rapids.^[60][61] The freeway remains listed as a part of the Interstate Highway System as I-296 however.^[16]

The next section of freeway opened between Howard City and Stanwood in 1980.^[62] Another segment was opened farther north, bypassing Big Rapids by 1984. The former route through town and a section of M-20 were designated as a business loop at the same time. US 131 followed 19 Mile Road between the end of the freeway and the former routing north of town.^[63] The gap was filled in when the freeway segment between Big Rapids and Osceola County was opened in 1986. The section of highway along 19 Mile Road was transferred to the Big Rapids business loop to connect it back to the new freeway.^[63] When the expansions ended in the mid-1980s, it was expected that the US 131 freeway would end at the south side of Cadillac, "perhaps forever".^[9] MDOT had ended all consideration of additional freeway mileage in 1981, citing decreased gas tax revenues, decreased traffic and higher construction costs. A 1979 report said that while traffic forecasts showed continued growth, upgrades to existing roads would be sufficient to handle traffic needs.^[9]

One of the more unusual sections of the US 131 freeway in the Grand Rapids area is the S-Curve.^[64] This section of freeway carries US 131 over the Grand River with two sharp turns in the road. The design for this structure was completed in 1952 and placed the freeway on the least expensive land in the area, even though planners knew that the design would cause problems. As noted by the Grand Rapids Press in 1981, "the speed limit on the S-Curve must be reduced as low as 25 mph [40 km/h] on some bad-weather days because of the sharpenss of the turns and [the] numerous accidents [that] have occurred there."^[65]

On December 27, 1999, the state awarded a $85.7 million contract for the replacement of the S-Curve on US 131.^[64] Deposits of gypsum under the roadway were dissolving causing it to settle.^[66] A deteriorating bridge also forced the reconstruction of the freeway through the area.^[67] Construction began on January 15, 2000,^[45] diverting the 115,000 vehicles that used the stretch of road a day to find detours through the downtown area.^[68] As part of the project, a $1.2 million de-icing system was installed.^[69] The system is designed to spray a de-icing fluid on the roadway that will be tracked by car tires up to a mile (1.6 km) along the road surface. This fluid will melt ice at temperatures below −20 °F (−29 °C), the temperature at which salt stops working. Unlike salt, the non-corrosive de-icer does not harm the bridge, but it costs more. The system is designed to be activated manually or automatically through sensors along the road. The system will melt snow, though that does not mean plowing will not be needed on the S-Curve.^[69] The idea behind the de-icing system is to keep the pavement wet, preventing the formation of ice.^[70]

Construction delays were caused by river flooding during spring rains. One design mistake meant that one of the bridges in the structure was built a foot (30 cm) too low, and Grandville Avenue was lowered to compensate for the error. The first northbound lanes were opened to traffic in mid-August, three weeks ahead of schedule. Before that opening, a ribbon-cutting ceremony was held on the freeway to allow local residents to walk along the structure on August 12.^[68] The remaining lanes opened to traffic on October 26, also ahead of schedule. When completed, there was an extra lane in each direction.^[71] Additional work started after the main roadway opened, by closing various ramps for reconstruction. This work also focused on restoring parking lots located under or adjacent to the freeway and testing the de-icing system,^[72] and the final ramps were opened in early December 2000 and early January 2001.^[73] The end results of the construction produced a freeway design that increased the rated traffic speed from 45 to 50 mph (72 to 80 km/h).^[66]

MDOT approved a $3.5 billion, 10-year transportation plan in 1986 that included an extension of the US 131 freeway north to Manton.^[74] Construction started on the Cadillac bypass in 1999.^[75] The first section was opened to traffic in November 2000. This 3.5-mile (5.6 km) southern segment ran from US 131 south of town to the M-55 east of downtown. US 131 remained routed through the downtown, but M-55 was rerouted to the bypass.^[76] Local residents were allowed to use the northern section of the bypass for recreational activities up until it was opened to traffic. The full 9.2-mile (14.8 km) bypass around Cadillac was dedicated to Sidney Ouwinga in a ceremony on October 27, 2001 and the road was opened to traffic on October 30, 2001. The former routing through town was redesignated BUS US 131 at the same time.^[77] Ouwinga was a state lawmaker who died in 1991 while serving in the Michigan House of Representatives. He was also a member of the US 131 Association that promoted further northern extensions of the freeway.^[78] The 10.5-mile (16.9 km) freeway expansion^[77] north around the city of Manton was opened in 2003. The former routing in were redesignated as a business loop at the time.^[79] The two bypasses cost $146 million to complete.^[77]

Constantine bypass maps

MDOT's planning maps for the bypass
(click to enlarge, north is to the right)

Originally, MDOT and its predecessor agencies had planned to convert US 131 into a freeway all the way north to Petoskey. They proposed adding the highway to the Interstate Highway System in the late 1960s when the federal government took proposals for additions to that system.^[57] While further northerly extension of the freeway from Manton toward Kalkaska and beyond was postponed by the MDOT in the 1970s,^[59] and cancelled "perhaps forever" in the early 1980s,^[9] an attempt to revive the extension to Kalkaska was unsuccessful in 2000.^[80] A bridge replacement project over the Manistee River in 2009–10 spelled the end to any further consideration by MDOT. According to the local project director, "currently, the department has no plans [to expand the freeway]. Someday it may happen, but not in the foreseeable future."^[81]

Unlike the north, a southerly extension of the freeway to or near the Indiana state line is still under study. Improvements to the US 131 corridor from Portage to the Indiana Toll Road have been underway for several years and although a late-2005 decision by MDOT to not pursue a new controlled-access route through St. Joseph County seemed to put an end to that discussion, public outcry and backlash from local legislators caused the department to re-evaluate this decision.^[82] State House Speaker Craig DeRoche was critical of the original decision, citing the economic development benefit such a road would bring to the area in defense of the proposed freeway.^[83] The previous "no-build decision" was rescinded in April 2006.^[82]

MDOT has begun a project to upgrade a section of US 131 the length of 16.4 miles (26.4 km) in St. Joseph County,^[84] home of one of the most dangerous in Southwest Michigan for auto crashes.^[85] The Final Environmental impact statement for the project was published in mid 2008, and the preferred alternative consists of a two-lane road bypassing the village of Constantine. The new highway would maintain access to local roads in at-grade intersections, and the department would maintain jurisdiction of the old route through town.^[84] MDOT has stated that present traffic demands do not warrant the cost of a full freeway facility on a new alignment from the Indiana Toll Road to north of Three Rivers,^[86] stating that such a project would cost over $300 million to build.^[87] Construction plans were placed on hold after an announcement in June 2009 as various proposals around the state, including the Constantine bypass were shelved until funding issues could be resolved. In total, 137 road and bridge projects totaling $740 million were delayed to 2012 because the state could not match available federal funding to pay for the work.^[88]

Design plans for the new bridge over the St. Joseph River were announced in January 2011. The expected groundbreaking on the venture is scheduled for 2012 with completion in 2014. MDOT currently has $9 million of the projected $25 million to complete the Constantine bypass.^[89] Residents in the community are divided over the proposed five-mile (8.0 km) highway. Business owners look toward the 3,000 cars and trucks that pass through downtown Constantine each day for customers.^[90] Other residents that work outside of in small community are looking forward to decreased commutes.^[89]

US 131 bears a number of memorial designations in addition to the Sidney Ouwinga Memorial Bypass near Cadillac. One of the oldest is Mackinaw Trail. That name was a former Indian trail that ran from Saginaw to Mackinaw City and Sault Ste. Marie. By 1915, the name was moved to the roadway that was later numbered US 131.^[91] The Mackinaw Trail Association was formed that year to promote an all-weather highway between Grand Rapids and Mackinaw City, using a trout logo for the road. The name was to be officially applied to the highway in 1929, but the State Senate did not agree to the proposal. The official endorsement of the name came in 1959 after the opening of the Mackinac Bridge revitalized the idea.^[92]

During World War I, households would display a service flag if a family member was serving in the war. A blue star denoted a service member in action and a gold star symbolized someone who died in the military. In St. Joseph County, chapters of the Daughters of the American Revolution and the American Legion wanted to honor the local fallen soldiers. Using the flags as inspiration, they planted 100 black walnut and four Norway spruce trees along the road south of Three Rivers. Dedicated on May 4, 1924, this tribute was called the Gold Star Memorial Highway, and it ran for 1.5 miles (2.4 km) along what is now US 131 south of Three Rivers.^[93]

In 1921, the section of highway south of Kalamazoo was named as part of the Colgrove Highway. This designation included several other roads in the Lower Peninsula, all named in honor of Philip Colgrove, the first president of the Michigan Good Roads Association. Colgrove was also the Barry County prosecutor and a state senator in the late 19th century. No maps list the name although the original law remains on the books. The Michigan Legislature proposed a bill in 2000 that would have repealed the 1921 statute creating the Colgrove Highway, but the bill ultimately died, sparing the name.^[94]

In the age of the auto trails, it was common for highways to be named rather than numbered. Unlike the Lincoln Highway, one attempt to create such a trail failed in Michigan. School children in Anderson, Indiana wanted to honor James Whitcomb Riley, the poet from the Hoosier State, in 1926 with a highway that connected the country's summer and winter resort areas. The Michigan segment of the road was to follow what later US 131 through the state. The James Whitcomb Riley Association promoted the highway by painting white bands on telephone poles with the name of the road in orange letters that August and September. Two problems sunk the association's efforts in Michigan. The first was that the road already had a name, Mackinaw Trail. The association did not secure permission of the state highway commissioner, as was required by a 1919 Michigan law. That law made it illegal for any "association to delineate or mark any other routes or trails through the State of Michigan... unless the same shall be approved in writing by the State Highway Commissioner."^[95] Those in government would not support the efforts for these reasons, and the highway was removed from Michigan. That action ended the efforts of the national association, and the highway was disbanded by December 1926.^[95]

Another auto trail from the 1920s was called the Michigan Trail. This highway, in the words of historian LeRoy Barnett, "followed just about every major trunk line at that time in the Lower Peninsula and covered over a thousand miles [1,600 km] of state highways."^[96] The Michigan Trail started in Toledo, Ohio and ran to Detroit with branches from there that reached to New Buffalo, Grand Rapids, and Port Huron. Other segments included US 131 between Kalamazoo and Petoskey, US 31 between New Buffalo and the Straits of Mackinac and a route between Port Huron and Big Rapids. The highway failed as a concept because it lacked focus, and many of the segments of roadway already had assigned names.^[96]

The last name applied to US 131 in 2004 is related to the first. That year, Public Act 138 added an additional name to the Mackinaw Trail.^[97] The "Green Arrow Route-Mackinaw Trail" follows US 131 from the M-66 junction near Kalkaska to Petoskey.^[91] Residents of the state have questioned the wisdom of having a "compound road name whose signboards [would] be nearly as long as the highway itself."^[98]

MDOT operates a maintains a listing of historic bridges that include two that formerly carried US 131. In 1913, the State Trunk Line Act required the highway department to build and maintain bridges at the state's expense if they were included in the nascent highway system.^[99] One of the first of these state-built structures is the Division Avenue – Plaster Creek Bridge in Grand Rapids. The crossing is listed on the National Register of Historic Places (NHRP) for its architectural and engineering significance.^[100] Built as Trunk Line Bridge No. 3 over Plaster Creek in 1914 by the MSHD, the span cost $6,063.09.^[101] Division Avenue carried US 131 until the construction of the freeway through Grand Rapids in the 1960s. The bridge is a 50-foot-long (15 m), filled spandrel arch design that was modified in 1935 to widen the deck from the original 28 feet (8.5 m) to the current 43 feet (13 m).^[101] The structure was added to the NRHP on December 17, 1999.^[100]

The second bridge listed by MDOT is the crossing of the Little Muskegon River for 190th Avenue in southern Mecosta County. Like the Plaster Creek bridge, this structure was also built by the MSHD under the Trunk Line Act of 1913. Built in 1916–17, the 45-foot-long (14 m), 18-foot-wide (5.5 m), concrete through-girder bridge cost $9,956.63 to build. It was initially named Trunk Line Bridge No. 61.^[102] This span is the oldest concrete girder bridge designed by the MSHD.^[103] US 131 followed 190th Avenue over the river until a realignment shifted the highway to another route in 1927.^[104][105]

Milepost numbers reset at the Indiana–Michigan state line crossing.

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1.000 mi = 1.609 km; 1.000 km = 0.621 mi

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• Indiana State Road 13
• Special routes of U.S. Route 131
• U.S. Route 31

• US 131 at Michigan Highways
• US 131 at Michigan Highways Ends
• US 131 at US Highway Ends
• US 131 at CanHighways