[2] From its southern terminus, WIS 173 runs concurrently northward with County Trunk Highway N (CTH-N) for about 1.6 miles (2.6 km) to the northern end of its concurrency with CTH-N, as well as a junction with the eastern end of CTH-G at a T intersection in the unincorporated community of Valley Junction.

In Valley Junction, WIS 173 turns northeast and continues along that straight heading for just under 22 miles (35 km), until it almost reaches census-designated place of Babcock.

Continuing northeast for about 4.7 miles (7.6 km), and passing just northwest of the Monroe County Flowage reservoir, it reaches the unincorporated community of Norway Ridge.

Just under a mile (1.6 km) northwest of that community is WIS 173's junction with the eastern end of CTH-EW at a T intersection.

Nearly immediately after entering the Town of Kingston, WIS 173 passes through the unincorporated community of Mather, wherein it has two junctions with county trunk highways.

Running along the north side of the CN tracks, WIS 173 heads east-northeast for about 2.1 miles (3.4 km) until it reaches its junction with the southern end of CTH-D at a T intersection on the western edge of the unincorporated community of Cranmoor.

After continuing east-northeast along the south side of the CN tracks for roughly 1.7 miles (2.7 km), WIS 173 turns to head east again.