Chelsea Mi By MsOlson Period: Jan 1, 1845 to Jan 31, 1849 Mexican American War Timeline Jun 16, 1845 Texas Admitted to the Union Texas Congress accepts US's offer of annexation. Nov 1, 1845 US Tried to Buy Land (Slidell and Polk) President Polk sends Ambassador Slidell to Mexico to try to buy New Mexico and California. Mar 1, 1846 US Troops Stationed at Disputed Border General Tyler's army marches south into the territory claimed by both Mexico and the US. May 1, 1846 US Declares War President Polk receives a letter from General Tyler asking for congress to declare war. Congress approves a $10 million war budget, and 50,000 volunteers for the army. Feb 22, 1847 Battle of Buena Vista (La Angostura) Tyler's army of 5,000 defeats Santa Anna's army of 15,000 and forces them to retreat south. Sep 14, 1847 Mexico City Surrendered US army occupies Mexico City. Mar 10, 1848 Treaty of Guadelupe Hidalgo The treaty of Guadelupe Hidalgo was ratified by the U.S. Senate.