On November 3, 1804- Men of the Corps of Discovery began building Fort Mandan seven miles below the mouth of the Knife River on the north side of the Missouri (present-day Washburn, North Dakota), directly opposite the lower Mandan village. When the Corps’ task building the Fort was completed, the Frenchmen who had rowed and pulled the Corps’ boats upriver built their own canoes and headed downriver to St. Louis.
On November 4, 1804- Toussaint Charbonneau, a French trapper met with Lewis and Clark saying he wanted to join the Corps. He said he would bring along his two Shoshone teenage wives to serve as guides and interpreters and help the Corps secure horses from the Shoshone once they reached the Continental Divide. Lewis and Clark accepted and chose Sacagawea (or Sacajawea or Sakakawea) to accompany them.