What 1803 agreement more than doubled the size of the United States?

The Louisiana Purchase was the 1803 agreement that more than doubled the size of the United States.

The United States acquired approximately 828,000 square miles of territory from France for $15 million. The agreement was signed on April 30, 1803, and the United States took formal possession later that year. The land stretched from the Mississippi River to the Rocky Mountains and from the Gulf of Mexico toward the Canadian border.

President Thomas Jefferson initially worried that the Constitution did not clearly authorize purchasing territory, but he supported the deal because it secured control of New Orleans and the Mississippi River. The port was vital to farmers and merchants moving goods through the interior.

The purchase did not immediately settle every boundary or political question. It displaced Indigenous nations and intensified later debates about slavery, statehood, and federal expansion. Much of the acquired land eventually became part of fifteen states.