From Dillon, Montana, take Interstate Highway 15 south to Clark Canyon Dam, about 19 miles. Turn west, onto MT Highway 324, a paved, two-lane road that crosses the dam and skirts the reservoir along its northwest shore. Clark Canyon Reservoir, completed in 1963, is managed by the U.S. Bureau of Reclamation. The site of Lewis and Clark's Camp Fortunate is now under water, but an overlook, picnic site, and campgrounds have been developed above the shoreline, along the highway.
As you leave the reservoir, you will be driving west on Highway 324, up the Horse Prairie Creek Valley, which Lewis called Shoshone Cove (using the old term 'cove' for 'valley'). Along the way, you'll pass a little town called Grant, about 12 miles from Clark Canyon Dam. In this area, Lewis sighted the first Shoshone on horseback.
Drive about 21 miles west from Clark Canyon Dam, to the junction of Trail Creek Road, a gravel road joining Highway 324 from the west.
The road to Lemhi Pass, called Trail Creek Road, is a rough, gravel and dirt road. From Highway 324 to Lemhi Pass on the Continental Divide, the distance is about 12 miles. Except for the last 1.4 miles, the Trail Creek Road crosses private ranch land. Please respect private property along the road.
The last four miles of road in Montana below Lemhi Pass is usually closed due to snow from late November through early June. This segment of road is also extremely muddy and impassible when wet from snow melt or summer rain. The Forest Service plans to surface this road with gravel, to reduce the rutting and mud, but it will remain a narrow, single-lane mountain road.
History, Lewis And Clark