When Americans Fought for Monterrey

In 1846, following its annexation of Texas, the United States went to war with Mexico over disputed territory in the Southwest and to enforce its declared southern boundary with Mexico: the Rio Grande. The U.S. president, James K. Polk, had campaigned on a policy platform of territorial expansion and sought to establish the United States as a hemispheric power. Polk coveted Californiaand its natural, deepwater harbors — especially San Francisco.