After crossing the county line, WYO 789 travels north for about 6 miles (9.7 km) where it reaches exit 187 of I-80/US 30.

US 287/WYO 789 continue in a northwest direction, passing through the towns of Jeffrey City and Sweetwater Station.

From the Washakie county line, the highway travels approximately 21 miles (34 km) before crossing the Big Horn River into Worland where it joins US 16/US 20.

At that point, WYO 789 separates from the concurrency of US 14/US 16/US 20 and returns to its northern path along with US 310 for about 28 miles (45 km) to the town of Lovell.

Just to the north of Frannie, US 310/WYO 789 bends slightly to the west, so that the road is actually inside Park County by about 400 feet before reaching the Montana state line.

WYO 789 was part of a 1950s proposal for a border-to-border U.S. Route 789 that would have traveled from Nogales, Arizona, to Sweet Grass, Montana.