Complex sentence: When Abraham Lincoln won the 1860 election on a platform of no new slave states, the South broke away to form the Confederacy; the first six states to secede held the greatest number of slaves in the South.
Split into simpler sentences: When Abraham Lincoln won the 1860 election on a platform of no new slave states, the South broke away to form the Confederacy. The first six states to secede held the greatest number of slaves in the South.