 When the Lincoln Highway became U.S. Highway 30 in 1926 , the route was 358 miles ( 576 km ) long and passed through every town along the way . Starting in the 1930s , the route 's alignment began to be straightened . By the mid @-@ 1930s , it was routed west of Missouri Valley on old Iowa 130 . The US 30 alignment south of Missouri Valley became U.S. Highway 30 Alternate . By 1952 , it had moved south of Marshalltown and was replaced by Iowa 330 and a seventeen @-@ mile ( 27 km ) southern jaunt through Belle Plaine had been replaced by a straight road . In 1955 , a couple of routing changes occurred . In Cedar Rapids , it began its move to the south , avoiding the downtown area , and in Clinton , it was rerouted over the Gateway Bridge , allowing Iowa 136 to cross the Lyons @-@ Fulton Bridge . However , by 1957 , the old alignment through Clinton and across the Lyons @-@ Fulton Bridge was numbered U.S. Highway 30 Alternate . 
