Following annexation and the close of the U.S.-Mexican War, Americans flooded into the newest addition to the United States in unprecedented numbers. During the three years from 1847 to 1850, more than 70,000 people came into Texas. During the decade that followed, another 400,000 followed. By the eve of the American Civil War, four out of every five Texans had arrived in the region only after it became part of the United States.