Park at the Lake Minnewanka parking area and hike north along the lake crossing the inlet canal (old Cascade River) over a foot bridge. Take the first marked trail (Stewart Canyon Trail) on the left and follow it up and down for about 20 minutes (along the canal) until you reach the mouth of a canyon. Before you enter the drainage itself, there is a narrow (not maintained-2008) trail on the right that heads east. Either take the narrow trail or just ascend the drainage up canyon. There will be some bushwhacking either way. Eventually you enter the narrow canyon outlet with a few bolted routes on your left. I advise skipping these first walls and continuing up canyon for the much nicer and less polished routes at the head of the canyon.
Black Feather Canyon, 5.9-5.12c, Lake Minnewanka, Banff National Park, Canadian Rockies, July, 2008