North Boundary Trail

North Boundary Trail is a 5.9-mile one-way traverse from the McGraw Ranch/Cow Creek Trailhead to the North Fork Trail junction beside the North Fork Big Thompson River. It starts with a short westward connector on Cow Creek Trail before turning north. This is not a loop, and the far junction has no road access. Allow about five to six hours for this leg; it gains roughly 2,555 feet and loses about 1,163 feet. Plan your return or an onward backcountry route before setting out; retracing the line makes an approximately 11.8-mile day. A separate West Creek Falls walk from the same trailhead is about five miles round trip and uses only part of North Boundary.

The route climbs from ponderosa pine into aspen and spruce, then steepens in a narrow gulch beneath granite domes. At the divide between Cow Creek and West Creek, the ridge opens to views north and south. Tight switchbacks descend toward West Creek; after crossing it, you reach the West Creek Falls Trail junction. The falls hike is a shorter, separate objective rather than the full North Boundary traverse.

Past the falls junction, rocky openings bring the Mummy Range into view. The hardest sustained stretch climbs nearly 1,300 feet in about 1.5 miles toward a narrow crest, with valley views along the way. An open meadow with wildflowers and a tall pine makes a strong foreground for the Mummy Range. The trail then drops through mixed pine, crosses an unnamed creek, and reaches the North Fork junction.

The McGraw Ranch/Cow Creek lot is off Devils Gulch Road, first-come, and limited to 15 passenger vehicles; there is no separate parking fee. In the West Creek Research Natural Area, daytime foot travel is allowed but discouraged; overnight stays and pack animals are prohibited there. Pets are prohibited on all park trails. This is a strenuous, high-elevation backcountry route, so the distant junction and return plan matter as much as the mileage.