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. On June 8, 1931, all of the Iowa portion of US 32 was absorbed into a newly extended US 6, which had previously connected Erie, Pennsylvania, and Cape Cod. The new US 6 also replaced US 38 in Nebraska and Colorado. By the end of 1937, US 6 extended from coast to coast. At the time, it and US 30 were the only cross country highways to bear a single route number across the country.