The city of St. Louis, Missouri is established.

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

Pike expedition: United States Army Lieutenant Zebulon Pike begins an expedition from Fort Bellefontaine near St. Louis, Missouri, to explore the west.

Lewis and Clark return to St. Louis after exploring the Pacific Northwest of the United States.

The Treaty of St. Louis is signed in St. Louis, Missouri.

Black Hawk War: Around three-hundred United States 6th Infantry troops leave St. Louis, Missouri to fight the Sauk Native Americans.

A fire threatens to burn St. Louis, Missouri to the ground.

Washington University in St. Louis is founded as Eliot Seminary in St. Louis, Missouri.

Nikola Tesla gives the first public demonstration of radio in St. Louis, Missouri.

The F4-strength St. Louis-East St. Louis Tornado hits in St. Louis, Missouri and East Saint Louis, Illinois, killing at least 255 people and causing $2.9 billion in damage (1997 USD).

The Louisiana Purchase Exposition World's Fair opens in St. Louis, Missouri.

Former President Theodore Roosevelt becomes the first U.S. president to fly in an airplane. He flew for four minutes with Arch Hoxsey in a plane built by the Wright Brothers at Kinloch Field (Lambert-St. Louis International Airport), St. Louis, Missouri.

The Great Flood of 1993 ends at St. Louis, Missouri, 103 days after it began, as the Mississippi River falls below flood stage.