In this transaction with France, signed on April 30, 1803, the United States purchased 828,000 square miles of land west of the Mississippi River for $15 million. For roughly 4 cents an acre, the United States doubled its size, expanding the nation westward.

In this treaty, signed on April 29, 1868, between the U.S. Government and the Sioux Nation, the United States recognized the Black Hills as part of the Great Sioux Reservation, set aside for exclusive use by the Sioux people.

Received April 28, 1917, this telegram was sent from the California Hop Growers Association, in protest of a proposed wartime ban on brewing beer.

This document lists and describes Robert E. Peary’s main sledge party which crossed the last 270 miles of ice to the North Pole; it consisted of Peary; Matthew Henson, who assisted Peary throughout nearly 20 years of polar explorations; and four Inuit, Ooqueah, Ootah, Egingwah, and Seegloo. This document is dated April 27, 1909, the day Peary returned to the ship that brought him home.

John Wilkes Booth, wanted for the assassination of President Abraham Lincoln, was found hiding in a barn near Bowling Green, Virginia, by a platoon of New York Cavalry and shot on April 26, 1865.

On April 25, 1945, American troops pushing eastward into Nazi Germany finally made contact with Russian forces pushing westward near the Elbe River.

In this once secret letter to President Harry S. Truman, Secretary of War Henry Stimson requested an urgent meeting to discuss the Manhattan Project, the all-out effort by the Federal Government to build an atomic bomb during World War II.