Timeline of the Lewis and Clark Expedition

This is the timeline of the Lewis and Clark Expedition through the American West, 1803–1806.

1802 DateEventDecemberThe Spanish ambassador in Washington, D.C., Carlos Martínez de Irujo, rejects the request of President Thomas Jefferson to grant Meriwether Lewis a passport to Spanish-held territories.

1803 DateEventJanuary 18President Jefferson sends a secret message to the U.S. Congress proposing an expedition to the Pacific Northwest.Ambrose, p. 59February 22The United States House of Representatives and Senate approve Jefferson's request.Ambrose, p. 60March 15Lewis travels to the U.S. Army arsenal in Harper's Ferry, Virginia (later West Virginia) to procure arms and ammunition for the expedition.Ambrose, pp. 84-90April 19Lewis arrives in Lancaster, Pennsylvania, where he studies the use of the sextant and chronometer for celestial navigation.Ambrose, p. 79-91April 30James Madison, Secretary of State, and Robert R. Livingston, U.S. Minister to France, reach an agreement to purchase the Louisiana Territory from France for $15 million.May 14Lewis leaves Lancaster and travels to Philadelphia to study medicine, anatomy and botany under the day's leading experts. During his three-week stay, he buys supplies and equipment as well as gifts for the Indians he expects to encounter.Ambrose, pp. 87-92June 19Lewis writes to William Clark inviting him to co-lead the expedition.Ambrose, p. 99June 20President Jefferson sends Lewis instructions for exploring the Louisiana Territory.July 4The proposed Louisiana Purchase Treaty is announced in Washington, D.C.July 15Lewis arrives in Pittsburgh, Pennsylvania, to direct the construction of a 55-foot keelboat with a 32-foot mast and benches for 22 oarsmen. He also purchases a pirogue over 40 feet long.Ambrose, pp. 102-107Discovering Lewis & Clark, KeelboatsJuly 18Clark writes to Lewis accepting his invitation.*Ambrose, p. 104August 31After more than a month of delays, the keelboat is completed and immediately loaded. With a crew of 11, Lewis heads down the Ohio River.Ambrose, pp. 105-107September 1Lewis documents the first day of travel, beginning what becomes the Journals of the Lewis & Clark Expedition.Lewis & Clark Journals, September 1, 1803Ambrose, pp. 108-110October 15Lewis rendezvous with Clark in Clarksville, Indiana territory. Clark is accompanied by his African-American slave York. Over the next two weeks, they select nine civilians from a field of volunteers.Ambrose, pp. 107-108October 20The U.S. Senate ratifies the treaty for the Louisiana Purchase.November 15While the Corps camps at the confluence of the Ohio and Mississippi Rivers, Lewis and Clark practice determining longitude and latitude using their surveying instruments.Lewis & Clark Journals, November 15, 1803November 28The expedition arrives at the U.S. Army post at Kaskaskia, Illinois, where they recruit more men.Lewis & Clark Journals, November 28, 1803November 30Governor Juan Manuel de Salcedo and former governor Sebastián Calvo de la Puerta y O'Farrill formally transfer the government of Spanish Louisiana to French governor Pierre Clement de Laussat in the capital New Orleans. Information is not conveyed to St. Louis, capital of Upper Louisiana, due to navigation being halted on the Mississippi during the winter. The area continues to be administered by the Spanish governor of Upper Louisiana, Carlos de Hault de Lassus.December 6Lewis travels by horseback to St. Louis in present-day Missouri intending to spend the winter procuring more supplies.Lewis & Clark Journals, December 6, 1803December 12Clark arrives at the site of the expedition's winter encampment on the Mississippi River above St. Louis in Illinois.Lewis & Clark Journals, December 12, 1803Discovering Lewis & Clark, December 12, 1803 De Hault de Lassus denies Lewis permission to sail upriver until the governor consults with his superiors.December 13Lewis begins construction of Camp Dubois while awaiting permission from de Hault de Lassus.December 20French governor Laussat transfers the Louisiana Territory to incoming U.S. governor William C. C. Claiborne in a New Orleans ceremony attended by U.S. general James Wilkinson.December 30Formal possession of the Louisiana Territory by the United States.

1804