A border clash between the United States and Mexico over disputed territory between the Rio Grande and Nueces Rivers, leaves eleven Americans dead. President James K. Polk asks Congress for a declaration of war. The House votes 174 to 14 for war on May 11, and the Senate adopts a war resolution the next day by a vote of 40 to 2. American troops capture the Mexican capital of Mexico City. By the Treaty of Guadalupe Hidalgo, Mexico, cedes its northernmost territory to the United States, lands that today include the states of California, Arizona, Utah,Nevada,New Mexico, Colorado, and Wyoming.