Approximately how many square miles did the Louisiana Purchase add to the United States?

The Louisiana Purchase added approximately 828,000 square miles to the United States. The territory covered much of the Mississippi River drainage basin west of the river.

The United States acquired the land from France in 1803 for $15 million. The purchase more than doubled the country’s area and extended U.S. claims across a large part of the continent.

The boundaries were not perfectly clear at the time, and the territory was not an empty wilderness. Many Native American nations lived across the region, and the United States later pursued treaties, removals, surveys, and military campaigns to assert control.

The purchase is sometimes described as acquiring all or most of the modern central United States, but its exact extent and the later division of the land into territories and states changed over time. The standard historical estimate remains 828,000 square miles.