The Louisiana Purchase (College Board AP® US History): Study Guide

Doubling the Size of a Nation

• America’s growing population wanted additional land space for settlement, farming, and other opportunities 

• The addition of new lands west of the Mississippi River doubled the size of the United States

The Louisiana Purchase

• In 1803, President Jefferson sent James Monroe to join Robert Livingston in France to negotiate with Napoleon, the leader of France

  • The aim was to buy any part or all of Florida and control the port of New Orleans for up to $10 million

• Napoleon offered to sell France’s entire land holdings west of the Mississippi River for $15 million

  • Monroe and Livingstone agreed to this, though they did not have the authority to do so

• The purchase went against Jefferson’s ideals of limited government and his beliefs as a strict constructionist

  • He thought a constitutional amendment was needed to complete the sale 

  • There was no part of the constitution which gave him the power to purchase territory

• James Madison, and others in Jefferson’s Cabinet, disagreed with him

  • They felt the deal was permitted under the Constitution’s rules about making treaties

  • The Senate agreed with Jefferson’s Cabinet and voted to sign the purchasing document after only two days of debate

• The treaty became official in late October 1803

  • It doubled the size of the United States

Exploration of the regions

• After the Louisiana Purchase, Jefferson ordered an exploration of the land purchased

• Meriwether Lewis and William Clark led the Corps of Discovery: 1804−1806 expedition 

  • Meriwether Lewis was chosen because he was the personal secretary of Thomas Jefferson

  • William Clark was chosen for his mapmaking skills

  • Both men had excellent survivor and hunting skills

• The expedition aimed to explore, map, and discover scientific knowledge about the northern region of the Louisiana Purchase

• Jefferson wanted Lewis and Clark to find the Northwest Passage, but this expedition proved there was no such route

  • Water to the east of the Continental Divide flows into the Atlantic Ocean or Gulf of Mexico 

  • Water to the west of the Continental Divide flows into the Pacific Ocean

• The expedition established friendly relationships with some of the Indigenous tribes in the region

  • A Shoshone woman named Sacagawea worked as an interpreter between the expedition and members of Indigenous groups to help acquire horses and other resources

• Zebulon Pike 1806−1807, led an expedition to the southern region of the Louisiana Purchase

  • He explored the Mississippi, Arkansas, and Red Rivers, along with parts of the Rocky Mountains in Colorado