U.S. Highway 6 (US 6) is an east–west U.S. Highway which runs 319 miles (513 km) across the U.S. state of Iowa. The route is signed in places as the Grand Army of the Republic Highway. The route begins at the Missouri River crossing at Council Bluffs. From there, it travels east to Atlantic. North of Atlantic, the highway overlaps Interstate 80 (I-80) until De Soto. Between De Soto and Adel, the highway overlaps US 169 before splitting off to the east towards Des Moines, where it closely follows the I-35 / I-80 corridor. At Altoona, the route again overlaps I-80 until Newton, where it splits away. The highway passes near or through several more cities before entering the Coralville / Iowa City area. From Iowa City, the highway heads to the east-southeast. Near Wilton, the route heads north to I-80 where it again overlaps to Davenport. At Davenport, US 6 then follows I-280 and US 61 before entering the city. On the eastern side of Davenport, it joins I-74 and enters Bettendorf before leaving Iowa for Illinois. Dating back to 1910, the route US 6 follows was originally part of the Great White Way and River-to-River Road auto trails which connected Council Bluffs and Davenport. When the U.S. Highway System was created in 1926, the highway was designated U.S. Highway 32. US 32 was renumbered in 1931 to US 6. As the Interstate Highway System expanded in the 1950-1970s, US 6's importance as a cross-state route was diminished by I-80. As a result, some sections of the route were moved onto I-80.

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