U.S. Federal Route 18 is a east-west highway across Northern Clayton County. This runs from the Clayton/Allamakee County Line, near Postville to the Iowa/Wisconsin State Line, near Marquette. U.S. Rt. 18 passes through the following towns in Clayton County. Luana Monona Froelich Giard Marquette
U.S. Rt. 18 is multi-plexed in Clayton County. U.S. Rt. 52, from the Allamakee/Clayton County Line to near Froelich. U.S. Rt. 18 intersects the following highways in Clayton County. U.S. Rt. 52, near Froelich. BUSN U.S. Rt. 18, near Mc Gregor. Iowa State Route 76, near Mc Gregor. BUSN U.S. Rt. 18, at Marquette.
Branches of U.S. Rt. 18 in Clayton County. A junction marker on EB BUSN U.S. Rt. 18/NB IA St Rt 76. A guide marker on SB IA St Rt 76. The Mississippi River at Marquette. EB U.S. Rt. 18 at the Iowa side of the bridge. EB U.S. Rt. 18 crossing the Mississippi River. EB U.S. Rt. 18 over the Mississippi River.
