The highway begins at an intersection with WIS 133 in Cassville, a village along the Mississippi River bordering Iowa, and runs northeastward from it.

It intersects County Trunk Highway U (CTH-U) in Beetown and then runs concurrently with WIS 33 along the Grant River west of Five Points.

[2] The highway runs southeasterly along the WIS 80 concurrency, intersecting with Business US 151 (Bus.

It then curves to the south, passing by Platteville Municipal Airport before exiting its concurrency with WIS 80 and running east from it.

The highway curves east in Newark before entering Beloit along Liberty Avenue.

After crossing the Rock River, the highway intersects US 51 before running northeast from it and terminating at an interchange with Interstate 39/Interstate 90 (I-39/I-90) and continuing as I-43.