"25 Apr 1846: U.S. and Mexican forces clashed at the Nueces River. The small American forces were defeated.
13 May 1846: U.S. Congress declared war on Mexico.
8 May 1846: The battle of Palo Alto occurred about eight miles northeast of Brownsville, Texas. U.S. forces, led by Major General Zachary Taylor, were victorious.
9 May 1846: Taylor's forces defeated the Mexican Army in Cameron County, near Brownville, Texas.
22 Feb 1847: U.S. forces successfully defended possession of a narrow mountain pass near Buena Vista, in northeastern Mexico.
17 Apr 1847: The Mexican Army under the leadership of Santa Ana, lost possession of a mountain pass, Cerro Gordo, near Jalapa,Mexico.
20 Aug 1847: American forces overtook the village of Churubusco, six miles south of Mexico City.
12 September 1847: General Scott led a successful attack against Chapultepec, a fortified hill guarding the gates of Mexico City.
14 September 1847: American troops entered Mexico City.
2 Feb 1848: The peace treaty was signed. Mexico gave the territories of California, New Mexico, and the Rio Grande region to the United States."
Timeline from: https://familysearch.org/learn/wiki/en/Mexican_War,_1846_to_1848