It runs from the Saskatchewan boundary (where it meets Highway 3) near Westgate to PTH 10 near Baden.

PTH 77 winds its way southeast through remote woodlands, traveling through Powell and Baden as well as crossing the Rice River, before entering the Rural Municipality of Mountain and coming to an end at an intersection with PTH 10 (Northern Woods and Water Route) just north of Mafeking along the banks of the Steeprock River.

[3] By 1963, it had been improved to a two-lane gravel road in its entirety, as well as being extended further west past the hamlet of Westgate to the Saskatchewan border, where it continued towards Armit as the newly opened Saskatchewan Highway 3 (Hwy 3).

[4] The highway was officially designated as Provincial Road 277 (PR 277) in 1966, as well as gaining a short spur to the community of Red Deer Lake.

[5] Becoming fully paved by 1983,[6] the highway was officially re-designated as PTH 77 in 1987, with the route changing very little since then.