Before the U.S. Numbered Highway System came into being in 1926, roads in Iowa were maintained and promoted by local organizations which sought to drive traffic into their communities. Two such organizations created virtually parallel routes connecting Council Bluffs and Davenport via Des Moines. The routes, the southern Great White Way and northern River-to-River Road, eventually merged into the Whiteway-7-Highway. The new route followed the Great White Way from Council Bluffs to Des Moines and the River-to-River Road from Des Moines to Davenport. In 2002, a group of residents from Adair, Casey, Menlo, Stuart, and Dexter formed a new group to promote the White Pole Road. Their intention was to bring visitors to their towns by diverting some traffic from the nearby I-80 / US 6 corridor to the south and onto the historic road. Poles were painted white up to high line along the drive. White Pole Road logo signs in each town give a short history of the town and their founders.
River-to-River Road {{Infobox road small The
River-to-River Road (
RRR) was also created in 1910 and also connected Council Bluffs and Davenport via Des Moines. This route, however, traveled a more northern route than the Great White Way. The route passed through
Neola,
Elk Horn,
Guthrie Center, Adel, Des Moines, Newton, Marengo, Iowa City, and Wilton. The route's origins trace back to the 1909–1910 winter season which brought, on average, of snow more than the previous year, which was followed by an unusually dry spring. Coupled with the advent of the
Ford Model T, many Iowans complained about the lack of good roads in the state. Governor
Beryl F. Carroll convened a
Good Roads convention on March 8–9, 1910, to discuss the condition of roads in his state. It was then that the route of the RRR was decided among the convention delegates. Further influencing the RRR corridor was an announcement from the
American Automobile Association that the annual
Glidden Tour would pass through Iowa. Governor Carroll arranged for farmers who lived along the route to
drag all of the road on the Saturday prior to the tour's arrival at precisely 9:00 am. Work was finished in one hour. When the highway commission started accepting registered routes, the RRR association planned to register their route as soon as possible. But miscommunication between association members and with the highway commission delayed the actual registration for years. The route became official on April 16, 1918. Eight months later, the Iowa State Highway Commission reversed course and restored Primary Road Nos. 2 and 7 to their original roadways. Although disappointed, the Whiteway-7-Highway Association responded by removing the number from their name. On November 27, 1925, the route officially became the Whiteway Highway.
U.S. Numbered Highways On November 11, 1926, members of the
American Association of State Highway Officials approved the plan to create a system of interstate highways across the country. Iowa's Whiteway Highway would take on the designation of US 32. For four-and-a-half years, US 32 spanned from Chicago to Council Bluffs. Meanwhile,
Roosevelt Highway Association was pushing to have US 6 extended westward. When the last segment of highway between Adel and Des Moines was paved in 1931, US 6 became the fourth paved road to cross the state. In the early 1940s, US 6 was the most heavily traveled route in the state. The state highway commission recorded that,
on average, over 1,900 vehicles used the road per day at any rural point. That compares to nearly 3,000 vehicles using US 6 daily in 2012. On April 29, 1947, the
Iowa General Assembly approved an act designating US 6 as the Grand Army of the Republic Highway, a distinction the route shares in other states. Governor
Robert D. Blue dedicated the Grand Army of the Republic Highway at the
Iowa Old Capitol Building on September 28, 1947. In attendance were the last two surviving Iowa veterans of the
U.S. Civil War. In the 1950s, the Iowa State Highway Commission began to straighten the route. A section of the highway between Grinnell and Ladora was straightened, which resulted in
Brooklyn and Victor being bypassed. Between Dexter and
West Des Moines, US 6 swapped alignments with
Iowa 90 in 1958. In 1961, US 6 was routed onto the new I-80 from the Iowa 90 interchange to the
Baxter exit, currently exit 159. Iowa 90 was extended onto the old US 6 alignment. However, in 1967, those changes were reversed and US 6 was taken off I-80 and put back on the road which had been Iowa 90. Iowa 90 was assigned the section of US 6 between what's now exit 106 along I-80 and exit 69 along I-35.
Abandoned sections Since the 1970s, portions of US 6 have been moved permanently onto I-80. The first section, between US 71 and Adair, was rerouted in 1972. The abandoned section became an extended Iowa 83 and CR G30 in
Adair County. In 1980, three lengthy sections were moved onto the Interstate: in western Iowa between Adair and Dexter, in central Iowa between Altoona and Newton, and in eastern Iowa between Wilton and Davenport. All three sections were originally kept as state highways, but, in 1991, when Iowa DOT first showed the new state highways' designations on the state highway map, the central section already had been turned over to
Polk and
Jasper counties. The western segment was numbered
Iowa 925 and the eastern segment Iowa 927. On July 1, 2003, between Dexter and Adel were turned over to Dallas County. US 6, which had previously split away from I-80 at the Dexter exit, was continued along I-80 to the US 169 interchange at De Soto, and then along US 169 to Adel. The former segments, Iowa 925 and Iowa 927, were turned over to their respective counties as well. ==Major intersections==