Clarissa G's Mexican American War Timeline By MsOlson Jun 16, 1845 Texas Admitted to the Union After separating themselves from the U.S, Texas admits themselves back to the Union. Period: Jun 16, 1845 to May 25, 1848 Clarissa G's Mexican American War Timeline Nov 1, 1845 US tries to buy land from Mexico President Polk sends John Slidell to Mexico to try and buy land from mexico but President Herrera decides not to meet with him. Mar 1, 1846 Us Troops Cross Disputed Border Polk instructs Taylor to take his army down the Nueces River to the Rio Grande where they ended up in disputed territory which angers the Mexicans. May 1, 1846 US declare war on Mexico Congress declares war on Mexico with 50,000 volunteers with the intent to intimidate Mexico. Sep 1, 1846 Col. Stephen Kearny leads army to add California to the US Col. Stephen Kearny heads off to annex California to the US because the US reconizes the successful trade routes in California. Sep 8, 1847 Battle of Molino del Rey US win this battle (led by General Scott) just outside of Mexico overpowering the population of their army by 6,500 soldiers. Sep 12, 1847 Mexico City surrenders Without the ability to get military aid, the Mexicans decide to surrender. May 25, 1848 Treaty of Guadelupe Hidalgo Congress enforces the Treaty of Guadelupe Hidalgo which allows more than half of of Mexico's territory to the US in exchange for $15 million.