 The highway ended at Main Street just blocks from the Mississippi River.In the mid-1920s, automobile associations continued to sponsor their named routes — there were 64 such named routes in Iowa — on top of the route numbers given by the state highway commission.This proved to be more confusing than helpful to the casual traveler, so in 1924, the American Association of State Highway Officials (AASHO, later AASHTO) called for a national system of interstate highways.