The Louisiana Purchase Doubles the Country
828,000 square miles for $15 million, and a president who doubted he could do it
Quick facts
- Year
- 1803
- Sold by
- France, under Napoleon
- Price
- $15 million for 828,000 square miles
- Effect
- Roughly doubled the size of the United States
What happened
President Thomas Jefferson sent negotiators to France hoping to buy the port of New Orleans and secure access to the Mississippi River. Napoleon, having given up his plans for a French empire in North America, instead offered the entire Louisiana Territory. In 1803 the United States purchased 828,000 square miles of land west of the Mississippi for $15 million, roughly four cents an acre, doubling the size of the country in a single treaty. Jefferson, normally a strict reader of the Constitution, privately doubted whether the federal government had the power to acquire new territory, but the chance to expand across the continent outweighed his misgivings. The purchase opened the way for the Lewis and Clark expedition and for decades of westward settlement.
Why it matters
The Louisiana Purchase set the United States on the path to becoming a continental power and made westward expansion the defining project of the nineteenth century. It also sharpened the coming crisis over slavery, because every new territory carved from this land raised the question of whether it would be free or slave, a question that ran straight toward the Civil War.
How we know
The Louisiana Purchase Treaty and its terms survive in the National Archives, and the negotiation is documented in the correspondence of Jefferson and his envoys Robert Livingston and James Monroe.
Sources
- National Archives. Louisiana Purchase Treaty (1803) · Primary source (author-declared)archives.gov · Cited as a "primary" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
- Office of the Historian, U.S. Department of State. Louisiana Purchase, 1803 · Reputable sourcehistory.state.gov · The domain "history.state.gov" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
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Part of a timelineHistory of the United States32 events · A hundred English colonists on a swampy island, a constitution argued out over one Philadelphia summer, a country that doubled its size for four cents an acre and fought a civil war over who counted as free, and the superpower that came out the other sideView all →