 US 30 bypasses Marshalltown approximately one @-@ quarter mile ( 400 m ) south of its business loop . Near Marshalltown Community College , it intersects Iowa 14 at a diamond interchange . The 18th Avenue interchange on the southeastern side of Marhsalltown is the eastern end of the business loop . From Marshalltown , it travels five miles ( 8 @.@ 0 km ) to Le Grand , crossing over the Overland Route rail corridor on the west side . It bypasses Le Grand to the north , where it intersects the northern end of Iowa 146 at a diamond interchange . Continuing east , the highway enters Tama County . It rises over a large hill north of Montour and then descends into the Iowa River valley . 
