Mexican–American War: Mexico ratifies the Treaty of Guadalupe Hidalgo, thus ending the war and ceding California, Nevada, Utah and parts of four other modern-day U.S. states to the United States for US$15 million.

The Mexican–American War, also known in the United States as the Mexican War and in Mexico as the United States intervention in Mexico, was an invasion of Mexico by the United States. It followed the 1845 American annexation of Texas, which Mexico still considered its territory because it refused…