Events from the year 1842 in the United States.

• President: John Tyler (I-Virginia)
• Vice President: vacant
• Chief Justice: Roger B. Taney (Maryland)
• Speaker of the House of Representatives: John White (W-Kentucky)
• Congress: 27th

• February 1 – Willamette University is established in Salem, Oregon.
• March – Commonwealth v. Hunt: the Massachusetts Supreme Court makes strikes and unions legal in the United States.
• March 5 – Mexican troops led by Rafael Vasquez invade Texas, briefly occupy San Antonio, and then head back to the Rio Grande. This is the first such invasion since the Texas Revolution.
• March 9 – First documented discovery of gold in California, by Francisco Lopez at Placerita Canyon in Rancho San Francisco, sparking a small-scale gold rush, mainly of Mexicans from Sonora.
• May 19 – Dorr Rebellion: Militiamen supporting Thomas Wilson Dorr attack the arsenal in Providence, Rhode Island but are repulsed.
• August 1 – A parade in Philadelphia celebrating the end of slavery in the Caribbean is attacked by a mob, leading to the 3-day Lombard Street riot.
• August 4 – The Armed Occupation Act is signed, providing for the armed occupation and settlement of the unsettled part of the Peninsula of East Florida.
• August 9 – The Webster–Ashburton Treaty is signed, establishing the United States–Canada border east of the Rocky Mountains.
• September – Ohio Wesleyan University is established in Delaware, Ohio.
• November 26 – The University of Notre Dame in South Bend, Indiana is established by Father Edward Sorin of the Roman Catholic Congregation of Holy Cross.
• December 20 – The Citadel, The Military College of South Carolina is established.

• The Sons of Temperance is founded in New York City.
• Founding of:
  • Cumberland University (in Lebanon, Tennessee)
  • Hollins University (in Roanoke, Virginia by Charles Cocke)
  • Villanova University (in Villanova, Pennsylvania by the Augustinian order)
  • Indiana University Bloomington
  • Indiana University Maurer School of Law
  • The Merchants Fund organization in Philadelphia^[1]
• The Scroll and Key secret society of Yale University is established.

• Second Seminole War (1835–1842)

• January 11 – William James, psychologist and philosopher (died 1910)
• January 21 – Henry Livermore Abbott, Union Army major and brevet brigadier general (died 1864)
• February 3 – Sidney Lanier, musician, poet and writer (died 1881)
• February 28 – Stephen Wallace Dorsey, U.S. Senator from Arkansas from 1873 to 1879 (died 1916)
• March 30 – John Fiske, philosopher (died 1901)
• June 16 – David Herold, accomplice of John Wilkes Booth (died 1865)
• June 24 – Ambrose Bierce, writer and satirist (died c. 1914 in Mexican Revolution)
• July 9 – Mary E. Smith Hayward, businesswoman and suffragist (died 1938)
• July 15 – James Hard, last verified living Union combat veteran of the American Civil War (died 1953)
• July 30 – Thomas J. O'Brien, politician and diplomat (died 1933)
• August 31 – Josephine St. Pierre Ruffin, African American civil rights campaigner and publisher (died 1924)
• September 13 – John H. Bankhead, U.S. Senator from Alabama from 1907 to 1920 (died 1920)
• October 3 – Frederick Rodgers, admiral (died 1917)
• October 14 – Joe Start, baseball first baseman (died 1927)
• October 28 – Anna Elizabeth Dickinson, orator (died 1932)
• December 15 – George Keller, architect (died 1935)

• January 4 – John W. Beschter, Jesuit priest and academic (born 1763 in Luxembourg)
• March 4 – James Forten, African American abolitionist and businessman (born 1766)
• March 13 – Samuel Eells, founder of Alpha Delta Phi fraternity (born 1810)
• July 23 – Timothy Swan, psalmist and hatter (born 1758)
• September 10 – Letitia Tyler, First Lady of the United States from 1841 to 1842 as wife of the 10th U.S. president, John Tyler (born 1790)
• October 2 – William Ellery Channing, Unitarian theologian and minister (born 1780)
• November 3 – Robert Smith, 6th United States Secretary of State (born 1757)
• December 1 – Philip Spencer, founder of Chi Psi fraternity and midshipman aboard USS Somers (born 1823)
• December 31 – George Cassedy, U.S. Representative from New Jersey (born 1783)

• Timeline of United States history (1820–1859)

• Media related to 1842 in the United States at Wikimedia Commons