Samantha M 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 A congressional resolution was signed by President Tyler to annex Texas Nov 1, 1845 US Tried to Buy Land (SIdel and Polk) President Polk instructs Sidel to go to Mexico to buy New Mexico and California from them Mar 1, 1846 US Troops Stationed at Disputed Border Taylor's army moves south into disputed territory claimed by both the US and Mexico. May 1, 1846 Us Declares War After Polk recieved Taylor's letter, he asked Congress to declare war on Mexico, which they approved. Sep 20, 1846 Battle of Monterrey Taylors army invades the city of Monterrey and defeats general Pedro de Ampudia's forces. This helps the US gain more troops for their army Sep 14, 1847 Mexico City Surrendered The US army claimed and occupied Mexico City. Feb 2, 1848 Treaty of Guadalupe Hidalgo The Treaty of Guadelupe Hidalgo is signed by negociators and then rushed to Washington for the Senate to ratify it.