Events of 1846

• January 5 - The United States House of Representatives votes to stop sharing the Oregon Territory with the United Kingdom.
• February 10 - Many Mormons begin their migration west from Nauvoo, Illinois, to Great Salt Lake led by Brigham Young.
• February 19 - In Austin, Texas the newly-formed Texas state government is officially installed.
• March 10 - Prince Osahito, fourth son of deceased Emperor Ninko of Japan, becomes Emperor Kōmei.
• April 25 - Mexican-American War: Open conflict begins over border disputes of Texas' boundaries.
• May 8 - Mexican-American War: The Battle of Palo Alto - Zachary Taylor defeats a Mexican force north of the Rio Grande at Palo Alto, Texas in the first major battle of the war.
• May 13 - Mexican-American War: The United States declares war on Mexico.
• 16 May - Under the leadership of British Prime Minister Robert Peel, the British Parliament repeals the Corn Laws, replacing the old Colonial mercantile trade system with Free Trade.
• May 17 - The Saxophone is patented by Adolphe Sax.
• May 25 - The Royal Geographical Society awards Paweł Edmund Strzelecki a Gold medal "for exploration in the south eastern portion of Australia".
• June 10 - Mexican-American War: The California Republic declares independence from Mexico.
• June 14 - Bear Flag Revolt begins - American settlers in Sonoma, California start a rebellion against Mexico and proclaim the California Republic.
• June 15 - 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.
• June 16 - Pope Pius IX succeeds Pope Gregory XVI as the 255th pope.
• July 7 - Acting on instructions from Washington, DC, Commodore John Drake Sloat orders his troops to occupy Monterey and Yerba Buena thus beginning the United States annexation of California.
• September 19 - The Virgin Mary is said to have appeared to two children in La Salette, France.
• September 23 - Discovery of Neptune: The planet is observed for the first time by German astronomers Johann Gottfried Galle and Heinrich Louis d'Arrest as predicted by the British astronomer John Couch Adams and the French astronomer Urbain Le Verrier, although the planet didn't get its current name for many years.
• October 1 - Christ College, Tasmania opens with the hope that it would develop along the lines of an Oxbridge college and provide the basis for university education in Tasmania. Today, it's the oldest tertiary instituition in Australia.
• December 28: Iowa is admitted as the 29th U.S. state.

Undated