During the winter of 1804-1805, Fort Mandan, named for nearby Indians, served as winter quarters for the Lewis and Clark Expedition. Captain Clark selected the site on November 2, 1804, and the fort was built in a triangular shape from local cottonwood logs with mud-chinked walls. Huts for men and supplies formed two sides, while the third was blocked by "amazing long pickets." The men moved into their unfinished buildings on November 16, and the two captains entered theirs four days later. Many visitors came there, including Toussaint Charbonneau and Sakakawea. During the winter, the captains learned as much as possible about the Missouri River tribes and the country ahead, while tools and equipment were mended for the Mandans in exchange for foodstuffs. On April 7, 1805, the keelboat and 11 men departed downriver under Corporal Richard Warfington, while that same day the rest of the party, consisting of the 2 captains and 31 others, set out upriver in "six small cancers, and two large peroques."