1840 in the United States

Events from the year 1840 in the United States.

Federal government

 * President: Martin Van Buren (D-New York)
 * Vice President: Richard M. Johnson (D-Kentucky)
 * Chief Justice: Roger B. Taney (Maryland)
 * Speaker of the House of Representatives: Robert Mercer Taliaferro Hunter (W-Virginia)
 * Congress: 26th

{| class="wikitable collapsible collapsed" ! Governors and lieutenant governors

Governors

 * Governor of Alabama: Arthur P. Bagby (Democratic)
 * Governor of Arkansas: James Sevier Conway (Democratic) (until November 4), Archibald Yell (Democratic) (starting November 4)
 * Governor of Connecticut: William W. Ellsworth (Whig)
 * Governor of Delaware: Cornelius P. Comegys (Whig)
 * Governor of Georgia: Charles J. McDonald (Democratic)
 * Governor of Illinois: Thomas Carlin (Democratic)
 * Governor of Indiana: David Wallace (Whig) (until December 9), Samuel Bigger (Whig) (starting December 9)
 * Governor of Kentucky: Charles A. Wickliffe (Whig) (until September 2), Robert P. Letcher (Whig) (starting September 2)
 * Governor of Louisiana: André B. Roman (Whig)
 * Governor of Maine: John Fairfield (Democratic)
 * Governor of Maryland: William Grason (Democratic)
 * Governor of Massachusetts: Edward Everett (Whig) (until January 18), Marcus Morton (Democratic) (starting January 18)
 * Governor of Michigan: Stevens T. Mason (Democratic) (until January 7), William Woodbridge (Whig) (starting January 7)
 * Governor of Mississippi: Alexander G. McNutt (Democratic)
 * Governor of Missouri: Lilburn W. Boggs (Democratic) (until November 16), Thomas Reynolds (Democratic) (starting November 16)
 * Governor of New Hampshire: John Page (Democratic)
 * Governor of New Jersey: William Pennington (Whig)
 * Governor of New York: William H. Seward (Whig)
 * Governor of North Carolina: Edward Bishop Dudley (Whig)
 * Governor of Ohio: Wilson Shannon (Democratic) (until December 16), Thomas Corwin (Whig) (starting December 16)
 * Governor of Pennsylvania: David R. Porter (Democratic)
 * Governor of Rhode Island: Samuel Ward King (Rhode Island)
 * Governor of South Carolina:
 * until April 7: Patrick Noble (Democratic)
 * April 7-December 9: Barnabas Kelet Henagan (Democratic)
 * starting December 9: John Peter Richardson II (Democratic)
 * Governor of Tennessee: James K. Polk (Democratic)
 * Governor of Vermont: Silas H. Jennison (Whig)
 * Governor of Virginia: David Campbell (Democratic) (until March 31), Thomas Walker Gilmer (Whig) (starting March 31)

Lieutenant governors

 * Lieutenant Governor of Connecticut: Charles Hawley (Whig)
 * Lieutenant Governor of Indiana: David Hillis (Whig) (until December 9), Samuel Hall (Whig) (starting December 9)
 * Lieutenant Governor of Illinois: Stinson Anderson (Democratic)
 * Lieutenant Governor of Kentucky: vacant (until September 2), Manlius Valerius Thomson (political party unknown) (starting September 2)
 * Lieutenant Governor of Massachusetts: George Hull (political party unknown)
 * Lieutenant Governor of Michigan: Edward Mundy (Democratic) (until month and day unknown), James Wright Gordon (Whig) (starting month and day unknown)
 * Lieutenant Governor of Missouri: Franklin Cannon (Democratic) (until November 16), Meredith Miles Marmaduke (Democratic) (starting November 16)
 * Lieutenant Governor of New York: Luther Bradish (Whig)
 * Lieutenant Governor of Rhode Island: vacant (until month and day unknown), Byron Diman (political party unknown) (starting month and day unknown)
 * Lieutenant Governor of South Carolina:
 * until April 7: Barnabas Kelet Henagan (Democratic)
 * April 7-December 9: vacant
 * starting December 9: William K. Clowney (Democratic)
 * Lieutenant Governor of Vermont: David M. Camp (Whig)
 * }

Events

 * January 13–14 – The steamship Lexington burns and sinks in icy waters, 4 miles off the coast of Long Island; 139 die, only 4 survive.
 * January 19 – Captain Charles Wilkes circumnavigates Antarctica, claiming what becomes known as Wilkes Land for the United States.
 * March 4 – Alexander S. Wolcott and John Johnson open their "Daguerreian Parlor" on Broadway (Manhattan), the world's first commercial photography portrait studio.
 * March 9 – The Wilmington and Raleigh Railroad is completed from Wilmington, North Carolina to Weldon, North Carolina. At 161.5 miles, it was the world's longest railroad at the time.
 * April – The Raleigh and Gaston Railroad is completed from Raleigh, North Carolina to near Weldon, North Carolina.
 * May 7 – The Great Natchez Tornado: A massive tornado strikes Natchez, Mississippi during the early afternoon hours. Before it is over, 317 people are killed and 109 injured. It is the second deadliest tornado in U.S. history.
 * November 7 – U.S. presidential election, 1840: William Henry Harrison defeats Martin Van Buren.

Ongoing

 * Second Seminole War (1835–1842)

Births

 * January 1 – Patrick Walsh, Irish-born U.S. Senator from Georgia from 1894 to 1895 (died 1899)
 * January 29 – Henry H. Rogers, financier (died 1909)
 * February 4 – Hiram Stevens Maxim, firearms inventor (died 1916)
 * February 9 – William T. Sampson, U.S. Navy admiral (died 1902)
 * March 5 – Constance Fenimore Woolson, fiction writer and poet (died 1894)
 * April 28 – Caroline Shawk Brooks, sculptor (died 1913)
 * May 1 –  Cynthia S. Burnett, educator, temperance reformer, and newspaper editor (died 1932)
 * May 4 – George Gray, U.S. Senator from Delaware from 1885 to 1899 (died 1925)
 * June 3 – Michael O'Laughlen, conspirator in the assassination of Abraham Lincoln in 1865 (died 1867)
 * June 6 – William Dudley Chipley, railroad tycoon and statesman (died 1897)
 * June 14 – William F. Nast, attaché, railroad executive and inventor (died 1893)
 * June 27 – Alpheus Beede Stickney, railroad executive (died 1916)
 * July 10 – Esther G. Frame, Quaker minister and evangelist (died 1920)
 * July 21 – Christian Abraham Fleetwood, Union Army 4th Colored Infantry Regiment soldier and Medal of Honor recipient (died 1914)
 * August 25 – George C. Magoun, railroad executive (died 1893)
 * August 28 – Ira D. Sankey, gospel singer and composer (died 1908)
 * September 10 – William B. Avery, Union Army soldier and Medal of Honor recipient (died 1894)
 * September 22 – D. M. Canright, Seventh-day Adventist minister and author, later one of the church's severest critics (died 1919)
 * September 27 – Alfred Thayer Mahan, U.S. Navy admiral, geostrategist and historian (died 1914)
 * September 23 – Simon B. Conover, U.S. Senator from Florida from 1873 to 1879 (died 1908)
 * October 1 – Anthony Higgins, U.S. Senator from Delaware from 1889 to 1895 (died 1912)
 * October 24 – Eliza Pollock, American archer (died 1919)
 * November 24 – John Brashear, astronomer (died 1920)
 * Earliest probable date – Crazy Horse (Tȟašúŋke Witkó), Chief of the Oglala Lakota (killed 1877)

Deaths

 * March 11 – George Wolf, politician (born 1777)
 * March 23 – William Maclure, geologist (born 1763 in Scotland; died in Mexico)
 * April 7 – Thaddeus Betts, U.S. Senator from Connecticut from 1839 to 1840 (born 1789)
 * August 10 – Seymour Brunson, early Mormon convert (born 1798)
 * August 27 – William Kneass, second Chief Engraver of the United States Mint from 1824 to 1840 (born 1781)
 * September 14 – Joseph Smith Sr., 1st Presiding Patriarch of the Latter Day Saint movement (born 1771)
 * September 18 – Constantine Samuel Rafinesque, French polymath (born 1783 in the Ottoman Empire)
 * June 14 – Anson Brown, lawyer and U.S. Representative from New York from 1839 to 1840 (born 1800)