U.S. Highway 6 (US 6) is an east–west U.S. Highway which runs 319 miles 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 through Oakland and 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. Through the Des Moines area, the highway runs about one mile north or south of the I-35 / I-80 corridor.
At Altoona, the route again overlaps I-80 until Newton, where it splits away from I-80. The highway passes near or through the cities of Kellogg, Grinnell, Victor, Marengo, the Amana Colonies, and Tiffin before entering the Coralville / Iowa City area. Through Coralville and Iowa City, US 6 has no direct access to I-80, I-380, or US 218; other routes like Iowa Highway 1 (Iowa 1) and Iowa 965 provide direct access. From Iowa City, the highway heads to the east-southeast through West Liberty and Atalissa. 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 the Great White Way and River-to-River Road. Both were 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 as US 6 was extended to the west coast. 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, the least-traveled sections of the route were moved onto I-80 and control of the vacated sections of highway was given to local jurisdictions.
[ Source: Wikipedia ]