 The highway enters Crawford County north of Dunlap in Harrison County . For seventeen miles ( 27 km ) , US 30 passes through farmland and the small communities of Dow City and Arion . For one @-@ half mile ( 800 m ) through Denison , it overlaps US 59 and Iowa 141 , which run concurrently through the town . The Iowa DOT refers to routes which overlap other routes as duplicate routes . It follows the East Boyer River through Denison as the Boyer River forks west of the northern intersection with US 59 / Iowa 141 . US 30 travels north @-@ northeasterly towards Vail . Between Vail and Westside , the highway ceases following the East Boyer River and heads due east towards Arcadia and Carroll in Carroll County . 
