On August 8, 1805, near today's town of Twin Bridges, Montana, the men were tediously poling their canoes up the river they called Jefferson's, which was becoming ever more "crooked with Short bends a fiew Islands and maney gravelly Sholes." That evening, Sacagawea shed the light of hope on the prospect of finally meeting her people, and securing horses for the portage over the mountains to the headwaters of the Columbia.
"The Indian woman," wrote Meriwether Lewis, "recognized the point of a high plain to our right which she informed us was not very distant from the summer retreat of her nation on a river beyond the mountains which runs to the west. This hill she says her nation calls the beaver's head from a conceived resemblance of its figure to the head of that animal."
Two days later, more than thirty miles upriver and ten miles south of today's Dillon, Montana, Lewis and three companions cooked lunch "under an immence high perpendicular clift of rocks" which, from the number of poisonous reptiles thereabouts, they called "the rattle snake clifts."
Some local people say that Sacagawea misspoke, that the so-called Beaverhead Rock resembles the animal only by the hyperextension of one's imagination, and that a rocky promontory opposite Rattlesnake Cliffs is the one she must have meant. Others say half the rocks in Beaverhead County resemble beavers' heads to some folks from certain angles, and that anyhow, we shouldn't tamper with legends. Admittedly, the resemblance is hard to recognize from the perspective of the modern highway, and at highway speeds.
Be that as it may, the compass bearings Clark took on August 13, 1805, from a point on the river about 14 miles south unmistakably identify this landmark as the feature she said was Beaverhead Rock. Furthermore, a mountain man's journal of 1831 also placed the well-known landmark here, near the mouth of the Ruby River, as did Montana pioneer Granville Stuart in about 1865.