1859 in the United States

Federal government

• President: James Buchanan (D-Pennsylvania)
• Vice President: John C. Breckinridge (D-Kentucky)
• Chief Justice: Roger B. Taney (Maryland)
• Speaker of the House of Representatives: James Lawrence Orr (D-South Carolina)
• Congress: 35th (until March 4), 36th (starting March 4)

January–March

• January 1 – Minting of Indian Head cent begins.
• January 10 – Lucy Cobb Institute opens in Athens, Georgia.
• January 28 – The city of Olympia is incorporated in the Territory of Washington.
• February 14 – Oregon is admitted as the 33rd U.S. state (see History of Oregon).

• February 27 – U.S. Congressman Daniel Sickles shoots dead Philip Barton Key for having an affair with his wife.
• March 2–3 – The Great Slave Auction, the largest single sale of slaves in U.S. history, with more than 400 people sold, takes place near Savannah, Georgia.
• March 21 – The Commonwealth of Pennsylvania issues the charter establishing the Zoological Society of Philadelphia, the first organization of its kind in the United States and founder of the nation's first zoo.

April–June

• April 4 – Bryant's Minstrels premiere the minstrel song "Dixie" (probably written by Dan Emmett) at Mechanics' Hall in New York City as part of their blackface show.
• April 20 – Daniel E. Sickles, a New York Congressman, is acquitted of the murder of Philip Barton Key on grounds of temporary insanity.^[1] The case marked the first successful use of the "temporary insanity" legal defense.^[2]
• June 8 – The discovery of the Comstock Lode in the western Utah Territory (present-day Nevada) sets off a rush of prospectors to the area.
• June 15 – The so-called Pig War border dispute between the Americans and the British on the San Juan Islands begins with the shooting of the namesake pig; the episode is resolved in October without human bloodshed.

July–September

• July – Pike's Peak Gold Rush begins in the Colorado Territory.
• July 1 – The first intercollegiate baseball game is played, between Amherst and Williams Colleges.
• August 1 – Andrew B. Moore is reelected the 16th governor of Alabama defeating William F. Samford.
• August 27 – Edwin Drake drills the first oil well in the United States, near Titusville, Pennsylvania, starting the Pennsylvanian oil rush.
• September – Joshua Abraham Norton proclaims himself "Emperor of the United States" in San Francisco.

October–December

• October 16 – Militant abolitionist leader John Brown raids the Harpers Ferry Armory in Harper's Ferry, Virginia, in an unsuccessful bid to spark a general slave rebellion.
• October 18 – Troops under Colonel Robert E. Lee overpower John Brown at the Federal arsenal.
• November 1 – The current Cape Lookout, North Carolina, lighthouse is lighted for the first time (its first-order Fresnel lens can be seen for 19 miles).
• December 2 – John Brown is hanged at Charles Town, West Virginia for his October 16 raid on Harpers Ferry.

Undated

• The Rancho Rincon de Los Esteros Land Grant is confirmed to Rafael Alvisa (part of modern-day Santa Clara County, California).
• The University of Michigan Law School is founded.

Ongoing

• Bleeding Kansas (1854–1860)