Manifest Destiny, the 19th-century doctrine that America's westward expansion was predetermined and inevitable wasn't named until later in the century, but it was the obvious course of U.S. politics when Lewis and Clark set off on their voyage. The West beckoned to men like Meriwether Lewis and William Clark, who were young, fit, courageous, confident, and willing to test their fortunes against it.

President Jefferson, who conceived and planned the Lewis and Clark expedition, believed that western tribes could be instrumental in the development of a fur-trade empire and would gradually be assimilated into white culture. If not, they would have to be removed to some other place.

White Americans believed that it was their God-given right to settle the West, and the path had to be cleared. Nineteenth-century Americans perceived the presence of Indian tribes all over the continent as an obstacle to settlement of U.S. territory — wherever whites chose to live.