Oliver A.'s Mexican American War Timeline By MsOlson Period: Jan 1, 1845 to Jan 1, 1849 Timespan Nov 1, 1845 U.S. Tried to Buy Land (Slidell and Polk) President Polk sends John Slidell to go buy New Mexico and California, but the mexican president, President Herrera, refuses to see him. Dec 29, 1845 Texas Admitted to the Union After the Congressional resolution to annex Texas is signed by President John Tyler and accepted on June 18th, Texas is finally admitted to the Union in December. Mar 1, 1846 U.S. Troops Stationed at Disputed Border General Taylor's Army travels towards the Rio Grande into disputed territory May 1, 1846 U.S. Declares War Polk gets a letter from Taylor asking him to declare war on Mexico. Sep 20, 1846 U.S. Victory in Monterey Taylor and his army storm the city and defeats the forces of General Pedro de Ampudia. Sep 13, 1847 Mexico City Surrendered The map is a diagram of the attack on Mexico City. Feb 2, 1848 Treaty of Guadalupe Hidalgo The Treaty of Guadalupe Hidalgo is made.