Wyoming Highway 51 travels from the eastern outskirts of Gillette at an interchange with I-90/US 14/US 16 (Exit 128) and the eastern terminus of I-90 BUS east to the town of Moorcroft. Highway 51 travels east, passing through the communities of Wyodak and Rozet, south of the Campbell County fairgrounds , coal mines, and south of Wyodak power plant. Wyoming 51 is the old alignment for US 14/US 16; and for most of its length closely parallels Interstate 90 which carries US 14/US 16. WYO 51 comes to an end at just under 25 miles at US 14/US 16/I-90 BUS.
WYO 51 is signed as a secondary state highway, but not marked from the Interstate 90 interchanges like most secondary state highway frontage roads.