What $15 million purchase in 1803 nearly doubled the size of the United States?

The $15 million purchase in 1803 that nearly doubled the size of the United States was the Louisiana Purchase.

The agreement transferred roughly 828,000 square miles from France to the United States. The territory stretched west of the Mississippi River to the Rocky Mountains and included land that later became all or part of 15 U.S. states. The deal was signed in Paris on April 30, 1803, and the United States took possession later that year.

President Thomas Jefferson initially sought access to New Orleans and the Mississippi River for western farmers. Napoleon Bonaparte unexpectedly offered the entire Louisiana territory after France's plans in North America weakened. The purchase price was $11.25 million, plus the United States' assumption of claims by American citizens against France, bringing the commonly cited total to $15 million.

The purchase is sometimes confused with the Alaska Purchase, which came from Russia in 1867. The Louisiana Purchase did not include all of the modern United States west of the Mississippi; its exact boundaries were disputed and later clarified through exploration and treaties.