The Louisiana Purchase doubled the amount of territory that could be claimed for expansion and settlement by future citizens, that could be explored and exploited for natural resources, and that could be useful in gaining protection against foreign powers.
The Louisiana Purchase added 828,000 square miles of territory to the area under the control of the United States government. The territory eventually was divided into all or part of the following states: Arkansas, Colorado, Iowa, Kansas, Louisiana, Minnesota, Missouri, Montana, Nebraska, North Dakota, Oklahoma, South Dakota, and Wyoming. Access to numerous valuable natural resources was obtained through the purchase, as demonstrated by the Lewis and Clark explorations.
Control of the Louisiana Territory had been secretly given back to Spain by France in 1800, but the United States government still understood that the area was under French control. As the importance of New Orleans as a shipping port increased for American merchants, concerns arose about the potential threats to trade and national security if the French maintained and increased their presence and power in the area. The United States threatened to ally itself with Great Britain against France in any future conflicts if control of New Orleans and surrounding territories could not be secured to the United States. As leader of France, Napoleon came to the conclusion that sale of the Louisiana Territory represented the most profitable way to prevent such an alliance.