Jason T's Mexican American War Timeline By MsOlson Period: Jan 1, 1845 to Jan 1, 1849 Mexican American War Mar 1, 1845 Texas Admitted to Union John Tyler signs bill to annex Texas into the union. Nov 5, 1845 US Tried to Buy Land (Sidel and Polk) John Sidell was sent to Mexico to try to purchase Texas land. Mar 1, 1846 US Troops Stationed at Disputed Border U.S. General Taylor moves his army to the Rio Grande May 1, 1846 U.S. Declares War When President Polk recieved General Taylors letter, Polk went to Congress and they declared war against Mexico. Sep 20, 1846 U.S. Victories - Battle of Monterrey General Taylors army invades Monterrey in attempt to cut off Northern Mexico Sep 14, 1847 Mexico City Surrendered This concluded the battle of Mexico City. Feb 2, 1848 Treaty of Guadelupe Hidalgo The Mexican negotiators signed it soon before it was rushed to Washington, DC.