President-José Mariano Salas
President-Valentín Gómez Farías
April 25 – Mexican-American War: Open conflict begins over border disputes of Texas' boundaries.
May 8 – Mexican-American War – 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 9 – Mexican-American War – Battle of Resaca de la Palma in Brownsville, Texas
May 13 – Mexican-American War: The United States declares war on Mexico.
June 10 – Mexican-American War: The California Republic declares independence from Mexico.
June 14 – Bear Flag Revolt: American settlers in Sonoma, California start a rebellion against Mexico and proclaim the California Republic.
July 7 – Acting on instructions from Washington, DC, Commodore
August 6 – José Mariano Salas assumed the presidency as provisional president.
August 22 – President José Mariano Salas decreed the Mexican Constitution of 1824 in effect again.
1846 in Mexico Wikipedia
Events in the year 1846 in Mexico.