1841
--March 4 – Martin Van Buren is succeeded as President of the United States by William Henry Harrison.
--March 9 – Amistad: The Supreme Court of the United States rules in the case that the Africans who seized control of the ship had been taken into slavery illegally
--April 4 – President William Henry Harrison dies of pneumonia, becoming the first President of the United States to die in office and at one month, the elected president with the shortest term served. He is succeeded by Vice President John Tyler, who becomes the 10th President of the United States.
--August 16 – U.S. President John Tyler vetoes a bill which called for the re-establishment of the Second Bank of the United States. Enraged Whig Party members riot outside the White House in the most violent demonstration on White House grounds in U.S. history.
--The city of Dallas, Texas is founded by John Neely Bryan.
1842
--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 31 – Middleton Junction and Oldham Branch Railway line opened up to Werneth in North West England.
1843
--May 22 – The first major wagon train headed for the American Northwest sets out with one thousand pioneers from Elm Grove, Missouri on the Oregon Trail.
--October 13 – In New York City, Henry Jones and 11 others found B'nai B'rith (the oldest Jewish service organization in the world).
--Abbeville, Louisiana is founded by descendants of Acadians from Nova Scotia.
1944
--February 28 – A gun on the USS Princeton explodes while the boat is on a Potomac River cruise, killing 2 United States Cabinet members and several others.
--March 12 – The Columbus and Xenia Railroad, the first railroad that is planned to be built in Ohio, is chartered.
--May 24 – The first electrical telegram is sent by Samuel F. B. Morse from the U.S. Capitol in Washington, D.C. to the B&O Railroad "outer depot" in Baltimore, Maryland, saying "What hath God wrought".
--June 15 – Charles Goodyear receives a patent for vulcanization, a process to strengthen rubber.
--June 27 – Joseph Smith, Jr., founder and first Prophet of The Church of Jesus Christ of Latter-day Saints (Mormons), and his brother Hyrum, are killed in Carthage Jail, Carthage, Illinois.
--August 8 – During a meeting held in Nauvoo, the Quorum of the Twelve, headed by Brigham Young, is chosen as the leading body of The Church of Jesus Christ of Latter-day Saints.
--December 4 – U.S. presidential election, 1844: James K. Polk defeats Henry Clay .
1945
--January 23 – The United State Congress establishes a uniform date for federal elections, which will henceforth be held on the first Tuesday after the first Monday in November.
--February 28 – The United States Congress approves the annexation of Texas.
--March 3 – Florida is admitted as the 27th U.S. state.
--The United States Congress passes legislation overriding a presidential veto for the first time.
--James K. Polk succeeds John Tyler as President of the United States.
--April 10 – A great fire destroys much of the city of Pittsburgh, Pennsylvania.
--July 4 – Near Concord, Massachusetts, Henry David Thoreau embarks on a 2-year experiment in simple living at Walden Pond
--In the United States Magazine and Democratic Review editor John L. O'Sullivan declares that foreign powers are trying to prevent American annexation of Texas in order to impede "the fullfillment of our manifest destiny to overspread the continent allotted by Providence for the free development of our yearly multiplying millions".
1946
--Mexican-American War
1947
--February 5 – A rescue effort, called the First Relief, leaves Johnson's Ranch to save the ill-fated Donner Party. These California bound emigrants became snowbound in the Sierra Nevada in the winter of 1846–1847, and some had resorted to cannibalism to survive.
--July 24 – After 17 months of travel, Brigham Young leads 148 Mormon pioneers into Salt Lake Valley, resulting in the establishment of Salt Lake City.
1948
--January 24 – California Gold Rush: James W. Marshall finds gold at Sutter's Mill, in Coloma, California.
--July 19 – Women's rights – Seneca Falls Convention: The 2-day Women's Rights Convention opens in Seneca Falls, New York and the "Bloomers" are introduced at the feminist convention.
--November 1 – In Boston, Massachusetts, the first medical school for women, The Boston Female Medical School (which later merges with Boston University School of Medicine), opens.
--November 7 – U.S. presidential election, 1848: Whig Zachary Taylor of Louisiana defeats Democrat Lewis Cass of Michigan in the first US presidential election held in every state on the same day.
--The Associated Press is established in NY
1849
--January 23 – Elizabeth B