The highway travels north from U.S. Route 2 (US 2) near Waterville through Withrow and east through Mansfield before ending at SR 17 at Sims Corner.

SR 172 begins as Road C NW at an intersection with US 2 at the unincorporated community of Farmer, between Waterville and Coulee City.

The highway travels north through farmland and serves Withrow before climbing Lone Butte and turning east into 14th Road NW.

[5] A gravel county road extending from Lone Butte through Mansfield to Sims Corner first appeared in a 1933 Department of Highways map of Washington.

[7][8] A paved road from Mansfield to Withrow and Farmer was built by 1950 and was signed as an extension of Secondary State Highway 10B (SSH 10B) in 1955.