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 , equivalent to in 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, , 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.