The South Boundary Trail is a 56.

8 km (35-mile) multi-day backcountry trail accessed from West Glacier via the historic Belton Bridge on Old River Road, offering access to the Middle Fork Flathead River valley and several remote creek drainages including Lincoln Creek, Harrison Creek, and Nyack Creek.

The trail features multiple backcountry campsites and junctions at 5. 3 miles (Lincoln Creek), 7. 2 miles (Harrison Creek), and 11. 8 miles (Nyack Creek), making it suitable for extended wilderness trips through a Big Game Wintering Area.

Bear spray is essential in this remote area, and hikers should be prepared for variable water availability and challenging terrain beyond the initial valley floor.