The significance of the Louisiana Purchase in expanding the United States was monumental, as it doubled the size of the nation in 1803. Acquired from France for $15 million, this vast territory stretched from the Mississippi River to the Rocky Mountains. The Purchase facilitated westward expansion, fostering exploration, settlement, and economic development. It provided crucial land for agriculture and resources, leading to increased migration and the establishment of new states. Additionally, it set the stage for future conflicts and conversations regarding slavery and governance as the nation grew.