 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.The first section of I-80 to open for traffic, from the West Mixmaster to the Douglas Avenue interchange in Urbandale, opened on September 21, 1958.