The Louisiana Purchase, completed in 1803, was significant for American expansion as it doubled the size of the United States, acquiring approximately 827,000 square miles of territory from France. This vast land acquisition opened up numerous opportunities for westward expansion, agriculture, and settlement, significantly contributing to the country's growth. It provided important resources and space for a growing population while also establishing the principle of Manifest Destiny—the belief that the U.S. was destined to expand across the continent. The Purchase fundamentally altered the nation's geography and politics, setting the stage for future conflicts over land and slavery.