Events January–March January 4 – Samuel Colt sells his first revolver pistol to the U.S. government. January 13 – The Treaty of Cahuenga ends fighting in the Mexican–American War in California. January 16 – John C. Frémont is appointed Governor of the new California Territory. January 17 – St. Anthony Hall fraternity is founded at Columbia University, New York City. January 30 – Yerba Buena, California, is renamed San Francisco. February 5 – A rescue effort, called the First Relief, leaves Johnson's Ranch to save the ill-fated Donner Party (California-bound emigrants who became snowbound in the Sierra Nevada earlier this winter; some have resorted to survival by cannibalism). February 22 – Mexican–American War: 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. February 25 – State University of Iowa is founded in Iowa City, Iowa. March – First known publication of the classic joke "Why did the chicken cross the road?", in The Knickerbocker, or New-York Monthly Magazine. March 1 The state of Michigan formally abolishes the death penalty. Faustin Soulouque is elected President of Haiti. March 4 – The 30th United States Congress is sworn into office. March 9 – Mexican–American War: United States forces under General Winfield Scott invade Mexico near Veracruz. March 14 – Verdi's opera Macbeth premieres at the Teatro della Pergola, in Florence, Italy. March 29 – Mexican–American War: United States forces under General Winfield Scott take Veracruz after a siege. April–June April 5 – The world's first municipally-funded civic public park, Birkenhead Park in Birkenhead on Merseyside, England, is opened. April 15 – The Lawrence School, Sanawar is established in India. April 16 – New Zealand Wars: A minor Māori chief is accidentally shot by a junior British Army officer in Whanganui on New Zealand's North Island, triggering the Wanganui Campaign (which continues until July 23). April 25 – The , carrying Irish emigrants from Derry bound for Quebec, is wrecked off Islay, with only three survivors from more than 250 on board. May – The Architectural Association School of Architecture is founded in London. May 7 – In Philadelphia, the American Medical Association (AMA) is founded. May 8 The Nagano earthquake leaves more than 8,600 people dead in Japan. Bahrain's ruler, Shaikh Mohamed bin Khalifa Al Khalifa,