In the winter of 1803–1804, President Thomas Jefferson sent two Virginians, Meriwether Lewis and William Clark, to lead the search for a navigable route through the American West to the Pacific Ocean, estimating that they'd be home within a year. He underestimated the task by about sixteen months, as Lewis and Clark endured a veritable American odyssey, blazing a 3,700-mile trail through a land previously known only to Indians and trappers.

Many sites along the Lewis and Clark National Historic Trail (which runs from Wood River, Illinois, to the Pacific Coast) have been established by the National Park Service, and from January 2003 till 2006 will take part in Lewis and Clark's bicentennial, giving “lewisandclarkers” the chance to follow in the footsteps of the great explorers, their thirty-three-man “Corps of Discovery,” and Sacagawea, their Shoshone guide and interpreter, who gave birth to a son (“Pomp”) along the way. Segments of the trail can be explored by foot, horse, bicycle, car, or boat, and patches remain where the landscape appears virtually unchanged since the explorers' journey. The notorious Lolo Trail through the Bitterroot Mountains on the border of Idaho-Montana remains almost as tough going today as then, when Lewis and Clark described it as the hardest test of the expedition.