When and where did the Lewis and Clark expedition begin?

Contrary to popular belief, the expedition DID NOT begin in St. Louis, Missouri. The first entry in the Lewis and Clark Expedition Journals state that the journey began in Pittsburgh, PA on August 30, 1803. Lewis, who had been assigned by Jefferson sailed down the Ohio River with supplies towards St. Louis.

William Clark would offer to join Lewis on the expedition weeks later on October 13, 1803 at Camp Dubois (in present-day Indiana). They then named their team the "Corps of Discovery." From there, they sailed down the Ohio River towards St. Louis. Meriwether Lewis had spent the time prior to their departure in St. Louis gathering information from mountain men returning from the west. They then departed St. Louis in May 1804 heading up the Missouri River.