February 22 - Mexican-American War: The Battle of Buena Vista
February 23 - Mexican-American War: Battle of Buena Vista
March 1 - The state of Michigan formally abolishes capital punishment.
March 9 - Mexican-American War: United States forces under General Winfield Scott invade Mexico near Vera Cruz.
March 29 - Mexican-American War: United States forces led by General Winfield Scott take Veracruz after a siege.
April 25 - The last survivors of the Donner Party are out of the wilderness.
May 7 - The American Medical Association (AMA) is founded in Philadelphia, Pennsylvania.
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. Celebrations of this event include the Pioneer Day Utah state holiday and the Days of '47 Parade.
July 29 - Cumberland School of Law founded in Lebanon, Tennessee, United States. At the end of 1847 only 15 law schools exist in the United States.
September 6 - Henry David Thoreau leaves Walden Pond and moves in with Ralph Waldo Emerson and his family in Concord, Massachusetts.
September 11 - Stephen Foster's well-known song, Oh! Susanna, is first performed at a saloon in Pittsburgh, Pennsylvania.
September 12 - Mexican-American War: the Battle of Chapultepec begins.
September 13 - Mexican-American War: Six teenage military cadets known as Niños Héroes die defending Chapultepec Castle in the Battle of Chapultepec. American General Winfield Scott captures Mexico City in the Mexican-American War.
September 14 - Mexican-American War: Winfield Scott captures Mexico City.
October 1 - German inventor and industrialist Werner von Siemens founds Siemens AG & Halske.
November 10 - The passenger ship Stephen Whitney is wrecked in thick fog off the southern coast of Ireland, killing 92 of the 110 on board. The disaster results in the construction the Fastnet Rock lighthouse.
November 12 - Sir James Young Simpson, a British physician, is the first to use chloroform as an anaesthetic.
November 19 - The second Canadian railway line, the Montreal and Lachine Railway, is opened.
November 29 - Whitman Massacre: Missionaries Dr. Marcus Whitman, his wife Narcissa, and 15 others are killed by Cayuse and Umatilla Indians, causing the Cayuse War.
December 5 - Jefferson Davis is elected to the US senate, his first political post.
