Lewis and Clark Expedition By 20BRCLAU Apr 30, 1803 Louisiana Purchase treaty signed Oct 20, 1803 The Senate ratifies the Louisiana treaty by a vote May 14, 1804 The exploers started up the Missouri River with small canoes May 31, 1805 The Corps reach the White Cliffs region of Missouri Jun 1, 1805 The Corps reach a fork in the Missouri and try to figure which way to go Jun 13, 1805 lewis reaches the Great Falls of the Missouri River Aug 18, 1805 Lewis celbrates his 31st birthday Aug 31, 1805 The expedition reaches sets out for the Bitterroot Mountains Nov 7, 1805 Clark wrote his journal "Great joy at camp" Sep 23, 1806 The expedition returned back to St.Louis