1847 in the United States

Federal government

• President: James K. Polk (D-Tennessee)
• Vice President: George M. Dallas (D-Pennsylvania)
• Chief Justice: Roger B. Taney (Maryland)
• Speaker of the House of Representatives:

John Wesley Davis (D-Indiana) (until March 4)

Robert Charles Winthrop (W-Massachusetts) (starting December 6)

• Congress: 29th (until March 4), 30th (starting March 4)

January–March

• January 4 – Samuel Colt sells his first revolver pistol, the Colt Walker, to the U.S. government for the Texas Rangers.
• January 13 – The Treaty of Cahuenga ends the fighting in the Mexican–American War in California.
• January 16 – John C. Fremont is appointed Governor of the new California Territory.
• January 17 – Saint Anthony Hall is founded at Columbia University in New York City.
• January 30 – Yerba Buena, California is renamed San Francisco, California.
• 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 have resorted to cannibalism to survive.
• February 22 – Mexican–American War – The Battle of Buena Vista: 5,000 American troops under General Zachary Taylor use their superiority in artillery to drive off 15,000 Mexican troops under Antonio López de Santa Anna, defeating the Mexicans the next day.
• March 1 – The state of Michigan formally abolishes the death penalty.
• March 9 – Mexican–American War: United States forces under General Winfield Scott invade Mexico near Veracruz in the first large-scale amphibious assault conducted by U.S. military forces.
• March 28 – The Massachusetts Donation of 1847 for Ireland sails from Boston on USS Jamestown.
• March 29 – Mexican–American War: United States forces led by General Winfield Scott take Veracruz after a siege.

April–June

• May 7 – The American Medical Association (AMA) is founded in Philadelphia.
• June 1 – Zeta Psi fraternity of North America is founded at New York University.
• June 10 – The Chicago Tribune begins publication.

July–September

• July 1 – The United States issues its first postage stamps, featuring George Washington and Benjamin Franklin.
• 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.
• July 29 – The Cumberland School of Law is founded at Cumberland University in Lebanon, Tennessee. At the end of 1847 only 15 law schools exist in the United States.
• August 12 – U.S. troops of General Winfield Scott begin to advance along the aqueduct around Lake Chalco and Lake Xochimilco in Mexico
• August 20 – U.S. troops defeat Mexican troops in Valencia, Mexico

October–December

• October 31 – Theta Delta Chi is founded as a social fraternity at Union College, Schenectady, New York.
• November 29 – The Whitman massacre: Oregon missionaries Dr. Marcus Whitman, his wife Narcissa, and eleven others are killed in the Oregon Country by Cayuse and Umatilla Indians, starting the Cayuse War.

Undated

• The North Carolina General Assembly incorporates the railroad town of Goldsborough, and the Wayne county seat is moved to the new town.
• The candy Necco Wafers are first produced as "hub wafers" in New England, an origin of the candy industry.
• Hardware business Orgill is established in Memphis, Tennessee.

Ongoing

• Mexican–American War (1846–1848)