US 310 starts at a junction with US 14, US 16, and US 20 west of Greybull; Highway 789 continues north along US 310 through the desert.

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

At the state line, Wyoming Highway 789 ends and US 310 continues northwest into the desert.

At the junction with Montana Highway 72, US 310 turns north, passing through farmland and the towns of Bridger and Fromberg before running concurrently with US 212.

The highway enters the city of Laurel, where US 212 continues onto I-90, and US 310 ends at Main Street.