On January 18, 1803 (yes, I know that’s one day ago, but close enough) Thomas Jefferson asked the United States Congress for money to finance the Corps of Discovery, the expedition led by Meriwether Lewis and William Clark that explored and mapped much of the western continental United States.
Reaching as far as Fort Clatsop, on the Pacific Ocean at the mouth of the Columbia River in present-day Oregon, Lewis and Clark’s expedition did much to shape the United States, both conceptually and physically. The expedition laid the groundwork for America to conceive itself as a continental nation, leading to the alluring notions of open land and the frontier.
In more practical terms, the two-year trip (1804-1806) helped the Americans lay claim to much of the western part of the continent before any European power could do so, giving them a distinct advantage in settling it and establishing control over the territory. Additionally, Lewis and Clark explored much of the land recently acquired in the Louisiana Purchase, making expansion there more viable.