The highway enters Crawford County north of Dunlap in Harrison County. For , US 30 passes through farmland and the small communities of Dow City and Arion. For 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.