U.S. Highway 75 (US 75) is a United States Highway in northwestern Iowa. It begins at the Missouri River on a bridge with Interstate 129 (I-129) and US 20. Immediately upon landing in Iowa from Nebraska, I-129 ends at an interchange with I-29. US 20 and US 75 continue around Sioux City on a four-lane expressway until US 20 exits to the east. US 75 heads to the north-northeast, parallel to the Floyd River, until Le Mars. There, Iowa Highway 60 (Iowa 60) continues northeastward on the expressway while US 75 heads due north. Near Hull, it is briefly overlapped by US 18. It leaves the state and enters Minnesota north of Rock Rapids. US 75 was one of the original U.S. Highways to be created in 1926, though its roots trace back nine years prior to the creation of the King of Trails, a 2,000-mile-long (3,200 km) auto trail that connected Winnipeg, Manitoba, and Galveston, Texas. In the Upper Midwest, there were two branches of the King of Trails that converged at Sioux City, which then continued south to Council Bluffs. In 1920, the Iowa State Highway Commission assigned route numbers to roads in order to improve wayfinding for travelers. The King of Trails was assigned Primary Road No. 12 (No. 12) from Council Bluffs to Sioux City and the western branch and No. 22 along the eastern branch. In 1926, the U.S. Highway 75 name was applied through Iowa to Primary Roads No. 12 and 22, the King of Trails route. In the 1950s, US 75's importance began to wane as I-29 was built along the Missouri River. As sections of the Interstate Highway opened up between Council Bluffs and Sioux City, US 75 were rerouted onto the new road. In 1984, the southern half of US 75 was removed from Iowa and rerouted into Nebraska. Today, the highway is still an important part of Iowa's highway system. In the late 1990s and throughout the 2000s, the highway along with Iowa 60 were improved into a continuous four-lane expressway between Sioux City and Minnesota.

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