The answer is Lincoln raised an army. With the vote in 1860
of Abraham
Lincoln, who competed on a message of covering slavery to where it now
existed, and the achievement of the Republican Party to which he went – the
first completely regional party in US history – in that voting, South Carolina separated
on December 20, 1860, the first state to ever formally separate from the United
States. Four months later, Georgia, Florida, Alabama, Mississippi, Texas and
Louisiana separated as well.
Under the treaty of the Guadalupe - Hidalgo , the Mexican American War ended in favor of the United States , this also relinquished the United States with 525,000 square miles of land from the Southern Border
