The trail into Big Spring Canyon begins at Squaw Flat Campground "A" on the south side of the road. It's not as well marked as it could be and my maps were confusing. The signs at the trailhead indicate destinations such as Squaw Canyon, Lost Canyon and Peekaboo but not Big Spring Canyon. I made a mistake and took the spur trail toward Campground B on the opposite side of the road before I figured out that was the wrong way. Turning back and crossing the road again I finally found Big Spring Canyon Trail, headed southwest.