In 1954, Coverdale & Colpitts, a New York City-based engineering firm working on behalf of the Iowa State Highway Commission, reported on the feasibility of building an east–west toll road, to be called the Iowa Turnpike, across the state. The firm found that the turnpike should closely parallel US 6 between Council Bluffs and Davenport. They concluded that the turnpike could be economically possible if $180 million ($ in ) in revenue bonds were issued at interest rates no higher than 3.5%.