Timeline of the Mexican-American War

The Events that Figured in the War from 1846-48

The Battle of Chapultepec
Library of Congress

The Mexican-American War (1846–1848) was a brutal conflict between neighbors largely sparked by the US annexation of Texas and their desire to take western lands such as California away from Mexico. The war lasted about two years in total and resulted in a victory for the Americans, who benefited greatly from the generous terms of the peace treaty following the war. Here are some of the more important dates of this conflict.


Mexico gains independence from Spain and difficult and chaotic years follow.


Settlers in Texas revolt and fight for independence from Mexico.

October 2: Hostilities between Texas and Mexico commence with the Battle of Gonzales.

October 28: The Battle of Concepcion takes place in San Antonio.


March 6: The Mexican army overruns the defenders at the Battle of the Alamo, which becomes a rallying cry for Texas independence.

March 27: Texan prisoners are slaughtered at the Goliad Massacre.

April 21: Texas gains independence from Mexico at the Battle of San Jacinto.


On September 12, Antonio López de Santa Anna is deposed as President of Mexico. He goes into exile.


March 1: President John Tyler signs the official proposal of statehood for Texas. Mexican leaders warn that annexing Texas could lead to war.

July 4: Texas legislators agree to annexation.

July 25: General Zachary Taylor and his army arrive in Corpus Christi, Texas.

December 6: John Slidell is sent to Mexico to offer $30 million for California, but his efforts are rebuffed.


  • January 2: Mariano Paredes becomes President of Mexico.
  • March 28: General Taylor reaches the Rio Grande near Matamoros.
  • April 12: John Riley deserts and joins the Mexican army. Because he did so before war was officially declared, he could not legally be executed later when he was captured.
  • April 23: Mexico declares defensive war against the United States: it would defend its territories under attack but not take the offensive.
  • April 25: Captain Seth Thornton's small reconnaissance force is ambushed near Brownsville: this small skirmish would be the spark that kicked off the war.
  • May 3–9: Mexico lays siege to Fort Texas (later renamed Fort Brown).
  • May 8: Battle of Palo Alto is the first major battle of the war.
  • May 9: Battle of Resaca de la Palma takes place, which results in Mexican army being forced out of Texas.
  • May 13: US Congress declares war on Mexico.
  • May: The St. Patrick's Battalion is organized in Mexico, led by John Riley. It consisted largely of Irish-born deserters from the US army, but there are also men of other nationalities. It would become one of Mexico's best fighting forces in the war.
  • June 16: Colonel Stephen Kearny and his army leave Fort Leavenworth. They will invade New Mexico and California.
  • July 4: American settlers in California declare the Bear Flag Republic in Sonoma. The independent republic of California only lasted a few weeks before American forces occupied the area.
  • July 27: Mexican President Paredes leaves Mexico City to deal with a revolt in Guadalajara. He leaves Nicolás Bravo in charge.
  • August 4: Mexican President Paredes is deposed by General Mariano Salas as chief executive of Mexico; Salas re-institutes federalism.
  • August 13: Commodore Robert F. Stockton occupies Los Angeles, California with naval forces.
  • August 16: Antonio Lopez de Santa Anna returns to Mexico from exile. The Americans, hoping he would promote a peace accord, had let him back in. He quickly turned on the Americans, stepping up to lead the defense of Mexico from the invaders.
  • August 18: Kearny occupies Santa Fe, New Mexico.
  • September 20–24: The Siege of Monterrey: Taylor captures the Mexican city of Monterrey.
  • November 19: US President James K. Polk names Winfield Scott as leader of an invasion force. Major General Scott was a highly decorated veteran of the War of 1812 and the highest-ranking US military officer.
  • November 23: Scott leaves Washington for Texas.
  • December 6: Mexican Congress names Santa Anna President.
  • December 12: Kearny occupies San Diego.
  • December 24: Mexican General/President Mariano Salas turns over power to Santa Anna's Vice-president, Valentín Gómez Farías.


  • February 22–23: The Battle of Buena Vista is the last major battle in the northern theater. The Americans will hold the ground they gained until the end of the war, but not advance any farther.
  • March 9: Scott and his army land unopposed near Veracruz.
  • March 29: Veracruz falls to Scott's army. With Veracruz under control, Scott has access to resupply from the USA.
  • February 26: Five Mexican National Guard units (the so-called "polkos") refuse to mobilize, rebelling against President Santa Anna and Vice-President Gómez Farías. They demand repeal of a law forcing a loan from the Catholic Church to the government.
  • February 28: Battle of Rio Sacramento near Chihuahua.
  • March 2: Alexander Doniphan and his army occupy Chihuahua.
  • March 21: Santa Anna returns to Mexico City, takes control of the government and reaches an agreement with the rebellious polkos soldiers.
  • April 2: Santa Anna leaves to fight Scott. He leaves Pedro María Anaya in the Presidency.
  • April 18: Scott defeats Santa Anna at the Battle of Cerro Gordo.
  • May 14: Nicholas Trist, charged with eventually creating a treaty, arrives at Jalapa.
  • May 20: Santa Anna returns to Mexico City, assumes the presidency once more.
  • May 28: Scott occupies Puebla.
  • August 20: The Battle of Contreras and the Battle of Churubusco open the way for the Americans to attack Mexico City. Most of the St. Patrick's Battalion is killed or captured.
  • August 23: Court-martial of members of St. Patrick's Battalion at Tacubaya.
  • August 24: Armistice is declared between US and Mexico. It would only last about two weeks.
  • August 26: Court-martial of members of St. Patrick's Battalion at San Angel.
  • September 6: Armistice breaks down. Scott accuses Mexicans of breaking the terms and using the time on defenses.
  • September 8: Battle of Molino del Rey.
  • September 10: Sixteen members of St. Patrick's Battalion are hanged at San Angel.
  • September 11: Four members of St. Patrick's Battalion are hanged at Mixcoac.
  • September 13: Battle of Chapultepec: Americans storm gates into Mexico City. Thirty members of St. Patrick's Battalion hanged within sight of the castle.
  • September 14: Santa Anna moves his troops out of Mexico City. General Scott occupies the city.
  • September 16: Santa Anna is relieved of command. The Mexican government attempts to re-group in Querétaro. Manuel de la Peña y Peña is named President.
  • September 17: Polk sends recall order to Trist. He receives it on November 16 but decides to remain and finish the treaty.


  • February 2: Trist and Mexican diplomats agree on the Treaty of Guadalupe Hidalgo.
  • April: Santa Anna escapes from Mexico and goes into exile in Jamaica.
  • March 10: The Treaty of Guadalupe Hidalgo is ratified by the USA.
  • May 13: Mexican President Manuel de la Peña y Peña resigns. General José Joaquín de Herrera is named to replace him.
  • May 30: The Mexican Congress ratifies the treaty.
  • July 15: The last US troops depart Mexico from Veracruz.

Sources and Further Reading

  • Foos, Paul. "A Short, Offhand, Killing Affair: Soldiers and Social Conflict During the Mexican-American War." Chapel Hill: University of North Carolina Press, 2002.
  • Guardino, Peter. "The Dead March: A History of the Mexican-American War." Cambridge: Harvard University Press, 2017.
  • McCaffrey, James M. "Army of Manifest Destiny: The American Soldier in the Mexican War, 1846-1848." New York: New York University Press, 1992.
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Minster, Christopher. "Timeline of the Mexican-American War." ThoughtCo, Apr. 5, 2023, thoughtco.com/timeline-of-the-mexican-american-war-2136188. Minster, Christopher. (2023, April 5). Timeline of the Mexican-American War. Retrieved from https://www.thoughtco.com/timeline-of-the-mexican-american-war-2136188 Minster, Christopher. "Timeline of the Mexican-American War." ThoughtCo. https://www.thoughtco.com/timeline-of-the-mexican-american-war-2136188 (accessed June 8, 2023).