 Construction on the Iowa Turnpike would never begin . In January 1956 , the Federal @-@ Aid Highway Act of 1956 ( H.R. <unk> ) was introduced in Congress . H.R. <unk> created the Interstate Highway System , a national system of controlled @-@ access highways . President Dwight D. Eisenhower signed the bill into law on June 29 , 1956 . The new law was problematic for the Iowa Turnpike for a couple of reasons . Firstly , the law designated 700 miles ( 1 @,@ 100 km ) of controlled @-@ access highway in Iowa , including a cross @-@ state route in the vicinity of the turnpike 's planned route . Secondly , the federal government was going to pay for ninety percent of the construction costs ; states were only required to match ten percent of costs ( however , tolls were generally prohibited ) . The Interstate Highway System 's completeness and financing rendered the Iowa Turnpike obsolete before it was ever constructed . 
