Alec G 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 signs the Congresional resolution to annex Texas Nov 1, 1845 US Tried to Buy Land (Sidel and Polk) President Polk sends John Sidell to Mexico with instructions to try to buy New Mexico and California. Mar 1, 1846 US Troops Stationed at Disputed Border General Taylor's army marches south, past the Nueces River toward the Rio Grande, moving into disputed territory claimed by both Mexico and the U.S. May 1, 1846 US Declares War President Polk asks the US Congress to declare war on Mexico. Feb 22, 1847 US Victories: Battle of Buena Vista General Taylor's army is outnumbered 15,000 to 5,000 but nevertheless, its firepower defeats Santa Anna's troops, and sends them retreating towards the south. Sep 12, 1847 Mexico City Surrendered Unable to get reinforcements, the Mexicans finally surrender. US troops capture and occupie Mexico City Feb 2, 1848 Treaty of Guadelupe Hidalgo Negotiators sign Treaty of Guadalupe Hidalgo.