During the Lewis and Clark exploration from 1804 to 1806, Captain William Clark mapped the route with only a sextant, chronometer, and compass, and this section of the Jefferson and Beaverhead river country records the party’s difficult search in August 1805 for the proper fork to follow. Journal entries by Clark, Lewis, Gass, Ordway, and Whitehouse recount exploration of multiple branches, notes left at the forks, reports that one branch was impracticable, and the decision to take the middle or left-hand branch. The party struggled through rapids, stones, islands, bayous, and willow-choked channels, at times cutting a passage through downed willows in the water, while hunting for Shannon and camping near streams later identified with the Wisdom River, Turf Creek, and nearby forks. When Clark returned through the area on July 11, 1806, strong southwest wind and the river’s crooked course hindered travel, and he reached the entrance of Wisdom River, where the party found a bayonet and the canoe left there the previous August still safe. The cartographic reconstruction traces the trail and changes in the river’s course over the last two hundred years and presents the southern upstream fork as the most probable course of the Wisdom River in 1805.