Louisiana Purchase: The United States purchases the Louisiana Territory from France for $15 million, more than doubling the size of the young nation.

The Louisiana Purchase is announced to the American people.

The United States Senate ratifies the Louisiana Purchase.

In New Orleans, Louisiana, Spanish representatives officially transfer the Louisiana Territory to a French representative. Just 20 days later, France transfers the same land to the United States as the Louisiana Purchase.

The Louisiana Purchase is completed at a ceremony in New Orleans.

Louisiana Purchase: In St. Louis, Missouri, a formal ceremony is conducted to transfer ownership of the Louisiana Territory from France to the United States.

Lewis and Clark Expedition: the "Corps of Discovery", exploring the Louisiana Purchase, suffers its only death when sergeant Charles Floyd dies, apparently from acute appendicitis.

After traveling through the Louisiana Purchase and reaching the Pacific Ocean, explorers Lewis and Clark and their "Corps of Discovery" begin their arduous journey home.

The Missouri Compromise is signed into law by President James Monroe. The compromise allows Missouri to enter the Union as a slave state, but makes the rest of the northern part of the Louisiana Purchase territory slavery-free.