Louisiana purchase : The Louisiana Purchase (French: Vente de la Louisiane, lit. 'Sale of Louisiana') was the acquisition of the territory of Louisiana by the United States from the French First Republic in 1803. In return for fifteen million dollars, or approximately eighteen dollars per square mile, the United States nominally acquired a total of 828,000 sq mi (2,140,000 km2; 530,000,000 acres) in Middle America.