Andrew Johnson
When Tennessee and ten other Southern slave states declared they were no longer part of the United States, he was the only member from among them to not quit his seat. Instead, he went to the U.S. and helped the North in the war, a so-called "Union Democrat". Despite being a Democrat, he was elected as Abraham Lincoln's Vice President on a "National Union" ticket in 1864, which thought the war should be ended and the south welcomed back into the union. Lincoln chose Johnson because he had been loyal but also thought it would be good to have a Democrat on the election ticket to show it was not a matter of party politics. Johnson freed his slaves in 1863, shortly before the law made it illegal. In 1865, Congress banned slavery in the entire U.S. just before the war ended.