The first minstrel show in the United States, The Virginia Minstrels, opens (Bowery Amphitheatre in New York City).

The Cathedral of Our Lady of Peace in Honolulu, Hawaii is dedicated. Now the cathedral of the Roman Catholic Diocese of Honolulu, it is the oldest Roman Catholic cathedral in continuous use in the United States.

President John Tyler signs a bill authorizing the United States to annex the Republic of Texas.

Manifest Destiny: US President James K. Polk announces to Congress that the United States should aggressively expand into the West.

In Austin, Texas the newly formed Texas state government is officially installed. The Republic of Texas government officially transfers power to the State of Texas government following Texas' annexation by the United States.

Mexican-American War: The United States declares war on Mexico.

Mexican-American War: President Mariano Paredes of Mexico unofficially declares war on the United States.

Bear Flag Revolt begins – Anglo settlers in Sonoma, California, start a rebellion against Mexico and proclaim the California Republic.

The Oregon Treaty establishes the 49th parallel as the border between the United States and Canada, from the Rocky Mountains to the Strait of Juan de Fuca.

Mexican-American War: American troops occupy Monterey and Yerba Buena, thus beginning the U.S. conquest of California.

U.S. forces led by Zachary Taylor capture the Mexican city of Monterrey.

Samuel Colt sells his first revolver pistol to the United States government.

Cumberland School of Law is founded in Lebanon, Tennessee, United States, one of only 15 law schools to exist in the United States at the end of 1847.

Cumberland School of Law is founded in Lebanon, Tennessee, United States, one of only 15 law schools to exist in the United States at the end of 1847.

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.

The United States annexes New Mexico.

Regular steamboat service from the west to the east coast of the United States begins with the arrival of the SS ''California'' in San Francisco Bay, 4 months 22 days after leaving New York Harbor.

Gadsden Purchase: The United States buys land from Mexico to facilitate railroad building in the Southwest.

Commodore Matthew Perry signs the Treaty of Kanagawa with the Japanese government, opening the ports of Shimoda and Hakodate to American trade.

Texas is linked by telegraph to the rest of the United States, with the completion of a connection between New Orleans and Marshall, Texas.

American adventurer William Walker departs from San Francisco with about 60 men to conquer Nicaragua.

American adventurer William Walker conquers Nicaragua.

Indian Wars: in Nebraska, 700 soldiers under United States General William S. Harney avenge the Grattan Massacre by attacking a Sioux village and killing 100 between men, women and children.

United States and Japan sign the Harris Treaty.

Daniel E. Sickles, NY congressman, is acquitted of murder on grounds of temporary insanity. This is the 1st time this defense is successfully used in the United States.

Pig War: Ambiguity in the Oregon Treaty leads to the "Northwestern Boundary Dispute" between U.S. and British/Canadian settlers.

Joshua A. Norton declares himself "Emperor Norton I" of the United States.

The first successful United States Pony Express run from Saint Joseph, Missouri to Sacramento, California begins.

The Prince of Wales (later King Edward VII of the United Kingdom) visits the United States.

South Carolina becomes the first state to secede from the United States.

Alabama secedes from the United States.

American Civil War: Georgia joins South Carolina, Florida, Mississippi, and Alabama in seceding from the United States.

American Civil War: Texas secedes from the United States.

American Civil War: Virginia secedes from the United States.

American Civil War: Confederate General Leonidas Polk invades neutral Kentucky, prompting the state legislature to ask for Union assistance.

The First Transcontinental Telegraph line across the United States is completed, spelling the end for the 18-month-old Pony Express.

American Civil War: Citing failing health, Union General Winfield Scott resigns as Commander of the United States Army.

American Civil War: Western Department Union General John C. Fremont is relieved of command and replaced by David Hunter.

American Civil War: Battle of Belmont: In Belmont, Missouri, Union forces led by General Ulysses S. Grant overrun a Confederate camp but are forced to retreat when Confederate reinforcements arrive.

American Civil War: The ''Trent Affair'': Confederate diplomatic envoys James M. Mason and John Slidell are freed by the United States government, thus heading off a possible war between the United States and Britain.