| January 10 | Poets Elizabeth Barrett and Robert Browning begin corresponding |
| January 23 | Uniform U.S. election day for president and Vice President authorized |
| January 29 | Edgar Allen Poe's "Raven" 1st published (New York City) |
| February 15 | William Parsons, Earl of Rosse, 1st uses 72" (183 cm) reflector |
| March 1 | President Tyler signs a resolution annexing the Republic of Texas |
| March 3 | 1st time, U.S. Senate overrides presidential (Tyler) veto |
| March 3 | Congress authorizes ocean mail contracts for foreign mail delivery |
| March 3 | Florida becomes 27th state |
| March 4 | James K. Polk inaugrated at 11th president |
| March 5 | Congress appropriates $30,000 to ship camels to western U.S. |
| March 14 | -5.3 degrees F (-20.7 degrees C) in Groningen |
| March 17 | Bristol man, Henry Jones, patents self-raising flour |
| March 17 | Rubber band patented by Stephen Perry of London |
| March 26 | Joseph Francis, New York City, patents a corrugated sheet-iron lifeboat |
| March 26 | Patent awarded for adhesive medicated plaster, precusor of bandaid |
| March 28 | Mexico drops diplomatic relations with US |
| April 2 | H L Fizeau and J Leon Foucault take 1st photo of Sun |
| April 10 | More than 1,000 buildings damaged by fire in Pittsburgh Pa |
| April 29 | Macon B. Allen and Robert Morris, Jr., 1st blacks to open law practice |
| May 2 | Domingo Sarmiento publishes "Civilizacion y Barbarie" |
| May 3 | 1st black lawyer (Macon B. Allen) admitted to bar |
| May 3 | Fire kills 1,600 in popular theater in Canton, China |
| May 14 | Utrecht-Arnhem Railway opens |
| May 17 | Rubber band patents |
| May 20 | 1st legislative assembly convenes in Hawaii |
| May 28 | Fire in Quebec Canada, 1,500 houses destroyed |
| June 1 | Homing pigeon completes 11,000 km trip (Namibia-London) in 55 days |
| June 4 | Mexican - U.S. war starts |
| June 12 | George Abernethy becomes 1st governor of Oregon Country |
| July 4 | Henry David Thoreau moves into his shack on Walden Pond |
| July 4 | Texas Congress votes for annexation to U.S. |
| July 14 | 1st postmasters' provisional stamps issued, New York City |
| July 14 | Fire in New York City destroys 1,000 homes and kills many |
| July 16 | New York Yacht Club holds its 1st regatta |
| September 10 | King Willem II opens Amsterdam Stock exchange |
| September 23 | 1st baseball team, New York Knickerbockers organize, adopt rule code |
| September 23 | Hunger strike in Hague |
| September 24 | 1st baseball team is organized |
| October 10 | Naval School (now called U.S. Naval Academy) opens at Annapolis |
| October 13 | Texas ratifies a state constitution |
| October 19 | Richard Wagners opera "Tannhauser," premieres in Dresden |
| October 20 | Opera "Tannhauser" is produced (Dresden) |
| November 4 | 1st nationally observed uniform election day in US |
| November 15 | Opera "Maritana" is produced (London) |
| December 27 | Ether 1st used in childbirth in U.S., Jefferson, Ga |
| December 29 | Texas admitted as 28th state |
