Events leading up to the Mexican War

  • Adams-Onis Treaty

    The Adams-Onis Treaty is signed by the U.S. and Spain. It established the border between the U.S. and Mexico and gave the U.S. Florida.
  • Mexico becomes independent from Spain

  • Consitution of Mexico enacted

    They officially name themselves the United States of Mexico, become a representative federal republic, and make Catholicism the national religion.
  • Declaration of the People of Texas

    The colonists declare that they will fight to have Mexico's 1824 constitution modified, and to become an independent Mexican state.
  • Texas declares independence from Mexico

    Texas declares independence and becomes the Republic of Texas.
  • U.S. recognizes Republic of Texas

  • House of Representatives approves Joint Resolution to annex Texas

  • President James Polk takes office

  • Texas votes in favor of their annexation

  • Texas joins the union

  • American soldiers stationed at the Rio Grande

    Polk orders Zachary Taylor to move his troops to the mouth of the Rio Grande. There they occupy land that Mexico had claimed as their own. Americans who were against the annexation of Texas and war with Mexico considered this to be a poor decision that ultimately instigated the war.
  • Mariano Parades y Arrillaga orders an attack

    Mariano Parades y Arrillaga (the dictator of Mexico at the time) orders an attack on Taylor's army at the Rio Grande. The commander at Matamoros delays the attack; instead of waiting, Parades firers him and gets a new commander.
  • Parades reorders the attack

  • Thornton Affair

    Mexicans attacked U.S. soldiers on U.S. side of the Rio Grande.
  • President Polk wants to declare war

    President Polk puts war declaration before Congress.
  • Congress approves the declaration of war

  • Mexico declares war