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Lewis and Clark
Survey of
Historic Sites and Buildings

National Historic Landmark Lemhi Pass

Location: On the Continental Divide in Lemhi County, Idaho, and Beaver head County, Mont. Along a rough, dirt road that extends east from Idaho 28 just south of Tendoy, Idaho, some 12 miles to the summit of the pass and then continues almost the same distance to its junction with Mont. 324. The junction occurs at a ranch on Trail Creek where the latter road switches from a general north-south to west-east direction about 22 miles west of I-15.

Probably no other area on the westbound route of the expedition is associated with so many events crucial to its success as is Lemhi Pass and vicinity. Moving through the pass in August 1805, the party crossed the Continental Divide, the first U.S. citizens on record to do so. At the same time, while passing from the upper reaches of the eastward-flowing waters of the Missouri drainage to the Pacific slope of the Rockies and the westward-wending waters of the Columbia system, the explorers also traversed the boundary of newly acquired Louisiana Territory and thus moved from the United States into a region claimed by various European powers.

Also, in the pass area, Lewis and Clark encountered the Shoshonis, the objective ever since leaving the Mandan villages, in present North Dakota, and upon whom all hopes of crossing the Bitterroot Mountains depended. Fortuitously, the chief of the band was Cameahwait, Sacagawea's brother, whom she reunited with at Camp Fortunate, Mont., east of Lemhi Pass; his village lay to its west. On August 30 the expedition, utilizing Indian guides, horses, and food, pushed northward from the Shoshoni village toward the Lolo Trail. On the return from the Pacific, neither the Lewis nor Clark elements of the expedition crossed Lemhi Pass.

Lemhi Pass
View from south to north across the shallow saddle of Lemhi Pass. The fence separates Montana, on the right, from Idaho, on the left, and traces the Continental Divide at this point. (National Park Service (Mattison, 1958).)

Unlike passes to the north and south that are traversed by improved roads and have accordingly been much changed by the hand of man, providentially Lemhi Pass (8,000 feet elevation), in a remote section of the Beaverhead Range, has remained almost in a pristine condition—all but unknown except to U.S. Forest Service employees, prospectors, ranchers, and an occasional student of the Lewis and Clark Expedition. From the summit, the same wild and majestic scenes that Lewis and Clark beheld still meet the eyes to the east and west.

Lemhi Pass
Lemhi Pass. (Beaverhead-Deerlodge National Forest.)

The only noticeable change is that, instead of the Indian trail they followed, the route is delineated by the narrow, dirt access road. At the crest of the pass itself, grassy, rolling slopes predominate, and visible in all directions are deep valleys and heavily timbered uplands. In the distance to the west and northwest, even in July, the snow-covered peaks of the Bitterroot and Salmon River Ranges glisten in the sky.

The eastern side of the pass is in Beaverhead National Forest, Mont.; the western, in Salmon National Forest, Idaho. Some of the land in the area is privately held or is claimed by miners and is used for ranching and prospecting. The eastern approach to the pass climbs a rather moderate slope; the western, via Agency Creek, a considerably steeper grade through frequent high canyon walls and an occasional narrow meadow.

The pass is unmarked, but the U.S. Forest Service has installed interpretive markers at the heads of the streams on the east and west sides of it that Lewis and Clark thought were the beginnings of the Missouri and Columbia Rivers. The Forest Service plans to reconstruct the dirt road from Tendoy, Idaho, to the pass to meet modern standards.

Last Updated: 22-Feb-2004