Robyn M's Mexican American War Timeline By MsOlson Jun 16, 1845 Texas Admitted to the Union President John Tyler helped to get Texas annexed but slavery stopped it from being a simple annextion. Nov 1, 1845 US tried to buy land Slidell was told to try and purchase California by President Polk, for $25 million but was refused by Mexico. Mar 1, 1846 US Troops Stationed at Disputed Border President Polk ordered troops to go to the border of Mexico and Texas, this increases the tension between the U.S. and Mexico. May 1, 1846 US Declares War President Polk declaration of war in hopes of gaining valuable territories in California and New Mexico. Apr 18, 1847 US Victories The Battle of Cerro Gordo, General Winfield Scott fought against Mexican armies and started a string of battles that resulted in the Capture of Mexico City. Sep 13, 1847 Mexico City Surrendered After 14 hours of fighting, the US army occupies Mexico City. Feb 2, 1848 Treaty of Guadelupe Hidalgo Called for Mexico to cede 55% of its territory in exchange for $15 million.