In 1803, President Thomas Jefferson signed a treaty with Napoleon Bonaparte that ceded a giant swath of land to the United States in the Louisiana Purchase. This doubled the size of America, giving the country access to the very important trade route of the Mississippi River and the port city of New Orleans. The land included in the Louisiana Purchase would eventually become thirteen new states of the Union for just pennies an acre.

The land of the New World had been under dispute between America, France, Great Britain, and Spain for decades already. At the start of the 19th century, France controlled New Orleans, but Spain had made a separate agreement to allow Americans to navigate the stretches of the Mississippi River. They claimed to control this passage to benefit both countries in trade. Napoleon's dream was to secure the entire area to use as a new economic center for France's conquest of Hispaniola (modern day Haiti) to trade in sugar, rum, and slaves. However, Napoleon was low on supplies, and concern about another war against Great Britain in Europe helped lead him to offer the land to Jefferson.

On 30 April 1803, the two leaders signed a Treaty of Cession, as well as papers regarding payment, to legally transfer the land. The property contained within the Louisiana Purchase stretched from the Gulf of Mexico to the amorphous north border with Canada, and from the Mississippi River to somewhere near the Rocky Mountains. It was an unbelievable 800,000 square miles (2 million square kilometers) of valuable resources for merely 60,000 francs, or 15 million dollars. Jefferson took a risk in engaging in this transfer, as it extended the power of the federal government over the states in testing the limits of the Constitution.

The largest single purchase of land in United States' history, the Louisiana Purchase included all or part of Montana, North Dakota, South Dakota, Minnesota, Wyoming, Nebraska, Iowa, Colorado, Kansas, Wisconsin, Missouri, Oklahoma, Arkansas and Louisiana, with perhaps a tiny bit for Texas and New Mexico. Extending the borders of the Union fulfilled the compulsion of Manifest Destiny to occupy the continent previously occupied by Native Americans. In 2003, many of these states celebrated the bicentennial of the Louisiana Purchase with special exhibits, parades, and fairs.