Wyoming Highway 345 begins its western end (or northern end at this point) at Montana Secondary Highway 451 at the Montana State Line, approximately 3 miles north of Parkman, Wyoming.

[3] For its entire length, WYO 345 parallels the Burlington Northern Santa Fe Railway and to some extent Interstate 90/US Route 87, which lies north of it.

Highway 345 travels through the census-designated place (CDP) of Parkman at about 3 miles, as it turns gently southeast.

Shortly after, the northern terminus of Wyoming Highway 343, which links to US 14 at Dayton, is met at just under 6 miles.

Highway 345 continues eastward toward Ranchester which it reaches nearing 12 miles and US 14 which provides access to exit 9 of Interstate 90.