At President Thomas Jefferson’s request, Meriwether Lewis and William Clark kept detailed journals during their 1804-1805 expedition from St. Louis to the Pacific Ocean. Jefferson sent the journals to the APS for safe keeping, where they remain today.

To prepare for the trip, Meriwether Lewis went to Philadelphia for instruction by Members of the APS. The expedition started near St. Louis in May, 1804 and reached the Pacific Ocean in November of 1805. They returned to St. Louis on September 23, 1806, having traveled 8,000 miles by boat, on foot, and on horseback.