 Despite the success of the seedling miles across the country , Iowa lagged behind other states in improving its roads . Before 1924 , Iowa 's 99 counties , not the state highway commission , were responsible for the construction and maintenance of the state 's roads . In the 1920s , road paving cost $ 30 @,@ 000 per mile ( $ 19 @,@ 000 / km ) , equivalent to $ 718 @,@ 000 per mile ( $ 446 @,@ 000 / km ) in 2016 dollars ; a major obstacle for county boards of supervisors that wanted to pave its roads . When counties could afford to build roads , the Iowa State Highway Commission required extensive grading to be done before paving . In 1922 , only five percent of Iowa 's roads , 334 miles ( 538 km ) , were paved . By 1924 , twenty percent of the Lincoln Highway in Iowa had been paved , and by 1931 , it was paved continuously from New York City to Missouri Valley , Iowa . 
