May 25— The expedition passes the small village of La Charette on the Missouri River. Charles Floyd writes in his journal that this is "the last settlement of whites on this river."
August 3—The Corps of Discovery hold the first official council between representatives of the United States and the Oto and Missouri Indians. They hand out peace medals, 15-star flags and other gifts, parade men and show off technology.
August 20—Sergeant Floyd dies, the only member lost during the expedition.
August 30—A friendly council with Yankton Indians held. According to a legend, Lewis wraps a newborn baby in a United States flag and declares him "an American."
September 7—The whole expedition drowns a prairie dog out of its den to send back to Jefferson.
September 25—The Teton Sioux (a subdivison of the Lakota) demand one of the boats as a toll for moving further upriver.
October 24—Expedition reaches the earth-log villages of the Mandans and the Hidatsas. The captains decide to build Fort Mandan across the river from the main village.
November 24 —Corps of Discovery takes the matter of where to spend the winter to vote. York, a slave, and Sacagawea, a woman, were allowed to vote. It was decided to camp on the south side of the Columbia River.
December 25 —Corps of Discovery moves into newly constructed Fort Clatsop to spend the winter.
March 23 —Corps of Discovery leaves Fort Clatsop on return voyage east.
July 27 —The Blackfeet Indians try to steal Lewis's group's rifles. A fight broke out and several Indians were killed. This is the first hostile encounter with an Indian tribe.
