Louisiana Purchase By ashlealeytham May 14, 1804 Expidition Begins The Corps of Discovery starts at the Missouri River Jul 24, 1804 Met Oto and Missouri Indians Aug 21, 1804 Reached Platte River Sep 25, 1804 Meeting with Sioux Indians Nov 20, 1804 Completed Fort Mandan for the winter Apr 7, 1805 Soldiers and rivermen are sent back to Jefferson to show what they have discovered May 26, 1805 Lewis first sees Rocky Mountains Jun 13, 1805 Expidition reaches Great Falls of Missouri River Aug 12, 1805 Lewis crosses the Continental Divide Oct 16, 1805 Expedition reaches the Columbia River Nov 15, 1805 Expedition reaches the Pacific Ocean Mar 23, 1806 Corps of Discovery heads home Jul 3, 1806 Expedition slipts up, going different paths. Aug 12, 1806 Expedition is reunited. Aug 23, 1806 Corps of Discovery reaches St. Louis