Before I-80 was planned, the route between Council Bluffs and Davenport, which passed through Des Moines, was vital to the state. Two competing auto trails, the Great White Way and the River-to-River Road, sought to be the best path to connect three of the state's major population centers. The two trails combined in the 1920s and eventually became U.S. Highway 32 (US 32) in 1926. US 6, which had taken the place of US 32, became the busiest highway in the state. In the early 1950s, plans were drawn up to build an Iowa Turnpike, to be the first modern four-lane highway in the state, along the US 6 corridor. Plans for the turnpike were shelved when the Interstate Highway System was created in 1956.