At the beginning of the New Nation period, the U.S. was unifying as a nation of states, but by the end of the period, our country was torn apart by a bitter civil war. The Democratic Party emerged under the leadership of Andrew Jackson, beginning the Jacksonian Era. We saw the birth and death of the Whig Party, and Abraham Lincoln became the first Republican president. During this period, the U.S. expanded west and fought a war with Mexico. Different sections of our country argued over the issue of slavery and its expansion into new territory. Compromises attempted to resolve sectional differences, but failed to stop the outbreak of the Civil War. In 1865, the 13th Amendment abolished slavery.