The National Route reenters Iowa on the Julien Dubuque Bridge (US 20), turning north onto Iowa 946 to reach US 52. In northern Sageville, the Great River Road turns north on CR C9Y, soon splitting onto Mud Lake Road, which, along with Circle Ridge Road, forms a loop back to CR C9Y in Sherrill. In Millville, the county road returns to US 52, which is followed into Guttenberg. As of 2012, the route through that city leaves US 52 east on Koerner Street, turning north on River Park Drive, west on Broadway Street, north on 2nd Street, west on Kosciusko Street, north on 3rd Street and through the municipal marina to CR X56. The Great River Road follows the entire length of CR X56 (including former Iowa 340) to McGregor, and then continues north on Iowa 76 and CR X52 (partly former Iowa 364) to Lansing, where the National Route crosses the Black Hawk Bridge (Iowa 9) to Wisconsin.