Hannah H 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 of the US agreed with congress to annex Texas. Nov 1, 1845 US tried to Buy Land (Slidell and Polk) President Polk sent Slidell to Mexico to buy California and New Mexico, but the Mexican Public found out so Slidell left without gaining California or New Mexico. Mar 1, 1846 US Troops Stationed at Disputed Border President Polk sent General Taylor and his troops to claim a base near the Rio Grande River in newly annexed Texas. May 1, 1846 US Declares War President Polk and Congress Declare war with Mexico, in addition Congress grants Polk $10 million and 50,000 volunteers to join the US force. May 1, 1846 Battle of Palo Alto General Taylor of the US won the battle; which was the first large battle between Mexico and the US. Sep 12, 1847 Mexico City Surrender After 14 hours of the US attacking and the trouble of getting reinforcements, Mexico City surrendered. May 25, 1848 Treaty of Guadelupe Hidalgo The US Senate ratified the treaty and then after about 2 months the Mexican Congress ratifies the treaty too.