James K. Polk, our 11th President, returned the country to Jacksonian-Democratic rule. He is most famous for the Mexican War (of which Lincoln was an adamant critic) and his expansionist policy in general. For his biography, you'd be best served reading "A Country of Vast Designs" by Robert Merry.
The James K. Polk Ancestral Home in Columbia, Tennessee is the only surviving residence of the eleventh U.S. President (excluding the White House). Samuel Polk, a prosperous farmer and surveyor, built the Federal-style brick house in 1816 while his oldest son James was attending the University of North Carolina. When the future President graduated in 1818, he returned to Tennessee and stayed with his parents until his marriage to Sarah Childress in 1824.