Background: What Led to the Louisiana Purchase?
In 1803, Napoleon Bonaparte had grand ambitions to conquer Europe. But to do so, he needed cash.
France had claimed area west of the Mississippi since the mid-1600s, but temporarily lost the land to Spain after the Seven Years’ War. Napoleon (who took power in 1799) re-secured the land but quickly found it too much trouble to manage; among other things, France had to contend with the Haitian Revolution in that Caribbean colony.
To help fund his war effort, Napoleon decided to sell France’s North American territories. His opportunity came in 1803, when Robert Livingston (US Minister to France) and James Monroe (former US Minister to France and future president) came to negotiate. The pair had been authorized by US President Thomas Jefferson to purchase New Orleans and the Floridas (then divided East and West) for $10 million.
Napoleon’s minister countered in a surprising way: He offered the entire Louisiana Territory (some 828,000 square miles) for $15 million. The Americans were only too eager to accept. Jefferson got quite the deal—just 4 cents per acre for all that land.
The purchase was something of quandary for Jefferson. As students of US history (or fans of the musical Hamilton) will recall, Jefferson ascribed to a strict interpretation of the Constitution. But he managed to waive those constitutional concerns given the opportunity before him. “I think it important in the present case to set an example against broad construction by appealing for new power to the people,” Jefferson wrote Senator Wilson Cary Nicholas. “If however our friends shall think differently, certainly I shall acquiesce with satisfaction, confiding that the good sense of our country will correct the evil of construction when it shall produce ill effects”
The Louisiana Purchase (bounded roughly by the Mississippi River in the east and the Continental Divide in the west) doubled the United States’ size. With all this newly acquired land, Americans were eager to explore this new frontier.
What States Came from the Louisiana Purchase?
The Louisiana Purchase included all of six modern states—Arkansas, Iowa, Kansas, Missouri, Nebraska and Oklahoma—as well as portions of nine others:
- Colorado: Area east of the Continental Divide
- Louisiana: Northern and eastern sections, including New Orleans
- Minnesota: Central and southern sections
- Montana: Area east of the Continental Divide
- New Mexico: Northeast corner
- North Dakota: Western and southern sections
- South Dakota: All but the northeastern tip
- Texas: Northern sections along the Oklahoma border
- Wyoming: Area east of the Continental Divide
If you have Canadian ancestry, you might notice the Louisiana Purchase also included parts of Alberta and Saskatchewan. The United States relented its claims to these strips of land to Great Britain in the Treaty of 1818 in exchange for the rest of modern Minnesota, North Dakota and South Dakota.
Historical Map: US Territory Acquired in the Louisiana Purchase
The map (created shortly after the purchase in 1804) assigns a different color to each state or territory, allowing you to distinguish between American, Spanish and British lands. Notice much of the western United States is still under Spanish control, and that the map indicates which American Indian tribes were prominent in each region.
The map also treats the Eastern United States in an interesting way. Though made in 1804, the map doesn’t feature the newly admitted state of Ohio. Rather, the land is still considered part of the “Western Territory.” Likewise, the relatively new Kentucky (admitted 1792) and Tennessee (admitted 1796) aren’t indicated as their own states. Their coloration suggests they’re still parts of Virginia and North Carolina, respectively.
Aftermath: The Louisiana Purchase and Your Family History
This map can provide valuable context as you chart your ancestors’ migrations across the United States. Were your ancestors pioneers braving a new frontier? Or did they stay in the relative safety of Eastern cities?
Shortly after the Purchase was finalized, Jefferson dispatched Meriwether Lewis and William Clark to explore the new land. Their “Corps of Discovery” returned with maps, reports of local native tribes, and “exotic” furs and animals.
They were eventually followed by traders and fur trappers, then scores of intrepid settlers who traveled along paths such as the Oregon and Mormon Trails. The advent of railroads and programs such as the Homestead Acts (1862) further encouraged settlement throughout the Heartland.
A version of this article was posted online in April 2018. Last updated: February 2026.
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