Conner B. Mexican American War timeline By MsOlson Period: Jan 1, 1845 to Jan 1, 1849 Mexican American War Mar 1, 1845 Texas Admitted to the Union President John Tyler admitts Texas into the union Nov 1, 1845 US Tried to Buy Land President Polk sent John Slidell to try to buy New Mexico and California from Mexico. Mar 1, 1846 US troops Staioned at Disputed Border General Taylor's army moved south into disputed territory May 1, 1846 US Declares War President Plok asked Congress to declare war on Mexico. They approve and send 50,000 men and $10 million towards the war. May 8, 1846 US Victories The US won both the Battle of Palo Alto and the Battle of Resaca De La Palma, which drove the Mexican Army across the Rio Grande. Sep 12, 1847 Mexico City Surrendered US forces storm Mexico city and after 14 hours of defending the Castle of Capultepec, the Mexican Army suurenders. Feb 2, 1848 Treaty of Guadelupe Hidalgo Negotiators sign the treaty, which gives the US Texas. the Rio Grande River was seen as the border from then on.