 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 ( $ 1 @.@ 59 billion in 2016 ) in revenue bonds were issued at interest rates no higher than 3 @.@ 5 % . 
