U.S. Route 6 in Iowa

U.S. Highway 6 (US 6) is an east–west United States Numbered Highway which runs 322 miles (518 km) across the U.S. state of Iowa. The route is signed in places as the Grand Army of the Republic Highway. Like all state highways in Iowa, it is maintained by the Iowa Department of Transportation (Iowa DOT). 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 toward Des Moines. Through the Des Moines area, the highway runs about one mile (1.6 km) 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 Iowa City metropolitan 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. Numbered Highway System was created in 1926, the highway was designated U.S. Highway 32 (US 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.

US 6 is a cross-state route that connects Council Bluffs and Davenport by way of Des Moines and Iowa City. The route parallels I-80 for most of its length; however, nearly one-third of the route overlaps the Interstate Highway. While the route is away from I-80, US 6 is a two-lane highway with a rural speed limit of 55 miles per hour (90 km/h). However, between Adel and Waukee, the roadway is a four-lane divided highway that has a speed limit of 65 mph (105 km/h).

US 6 crosses the Missouri River via the Grenville Dodge Memorial Bridge, named after the Union Army general during the U.S. Civil War, into Council Bluffs with I-480. Just three-quarters mile (1,200 m) into the state, I-480 ends at an interchange with I-29. US 6 heads east along I-29 south on the western side of Council Bluffs, then it overlaps I-80 and continues due east. On the east side of Council Bluffs, I-80 and US 6 split. Near Oakland, the highway follows the north–south US 59 for two miles (3.2 km). Near Lewis, the road turns to the north-northeast until it reaches Atlantic. In Atlantic, the route turns back to the east and heads toward downtown where it meets Iowa 83. US 6 / Iowa 83 travel together to the eastern side of Atlantic where they meet US 71. The three routes run together for four miles (6.4 km), when US 6 / US 71 split away from Iowa 83 and continue north to I-80. At I-80, US 6 leaves US 71 and joins I-80. At this point, US 6 begins the first of three instances when its traffic is routed along I-80. In the eastern part of Cass County, the two routes meet the northern end of Iowa 148.

As I-80 and US 6 approach Adair, the highways curve slightly to the south to bypass the community. There are two interchanges in Adair; both of the intersecting roads, at one time or another, carried US 6. County Road G30 (CR G30), the White Pole Road, was the original alignment of US 6, while CR N54 has not carried US 6 since 1980. Further east is an interchange with Iowa 25. About one mile (1.6 km) south of the interchange is Freedom Rock. Each year for Memorial Day, the rock is repainted with a patriotic scene by local artist Ray "Bubba" Sorenson II. Near Dexter, I-80 and US 6 graze the northwestern corner of Madison County. After two miles (3.2 km), the routes enter Dallas County and meet CR F60, another former alignment of US 6. Near the CR F90 / CR P58 interchange, they start heading northeast toward Des Moines. At De Soto, US 6 splits away from I-80 at the interchange with US 169.

At De Soto, US 6 turns to the north, overlapping US 169 for five miles (8.0 km) to Adel. East of Adel, US 6 is a four-lane divided highway for 14 miles (23 km), during which it passes through Waukee, Clive, and Urbandale along Hickman Road and intersects I-35 / I-80. Over the next two miles (3.2 km), it serves as the border between Urbandale and Windsor Heights. At 63rd Street in Des Moines, US 6 intersects Iowa 28. For one-half mile (800 m), US 6 / Iowa 28 run together on Hickman Road. Turning north, they run together for another mile (1.6 km) along Merle Hay Road, named after the first Iowa service member in World War I. At Douglas Avenue, US 6 splits away from Iowa 28 and continues east, becoming Euclid Avenue just west of the Des Moines River. In north-central Des Moines, it intersects US 69 and I-235. In northeast Des Moines, it turns to the northeast along Hubbell Avenue, which takes US 6 to Altoona. West of Altoona, it intersects US 65 and continues northeast passing the Adventureland theme park and Prairie Meadows casino. In northwest Altoona, US 6 intersects I-80 and US 65. Here, US 6 rejoins I-80 for the second time. After a third exit for Altoona, the Interstate resumes its 70 mph (115 km/h) rural limit. Near Colfax, the highways cross the South Skunk River. After an interchange with Iowa 117, the highway is forced to the north to avoid crossing the river multiple times. As the roadway returns south to its original line, it meets CR F48, which was another former alignment of US 6.

At Newton, US 6 splits away from I-80 at the Iowa 14 interchange. US 6 overlaps Iowa 14 for one-third mile (540 m). It turns off of Iowa 14 and enters the western side of Newton where it passes the Jasper County courthouse located in the downtown area. Between Newton and Grinnell, the route has more hills and curves. The highway crosses the North Skunk River near Kellogg. At Grinnell, it intersects Iowa 146 southwest of the Grinnell College campus. East of Grinnell, the route straightens out and is overlapped by US 63 for two miles (3.2 km) and by Iowa 21 for four miles (6.4 km). Near Victor, US 6 takes a northeasterly course through Ladora toward Marengo. At Marengo, it intersects the eastern end of Iowa 212. Five miles (8.0 km) east of Marengo is the western end of Iowa 20. Here, US 6 forms the southern leg of the Amana Colonies Trail. Three miles (4.8 km) later, it is joined by US 151 for two miles (3.2 km). US 6 heads to the southeast toward Tiffin and passes underneath I-380 but does not have direct access.