In January 1816, Polk was admitted into the University of North Carolina at Chapel Hill as a second-semester sophomore.
The Polk family had connections with the university, then a small school of about 80 students; Samuel was its land agent in Tennessee and his cousin William Polk was a trustee.
His father took him to see prominent Philadelphia physician Dr. The journey was broken off by James's severe pain, and Dr.
Ephraim Mc Dowell of Danville, Kentucky, operated to remove them. The operation was successful, but it might have left James impotent or sterile, as he had no children. His father offered to bring him into one of his businesses, but he wanted an education and enrolled at a Presbyterian academy in 1813.
Already involved locally as a member of the Masons, he was commissioned in the Tennessee militia as a captain in the cavalry regiment of the 5th Brigade.
He was later appointed a colonel on the staff of Governor William Carroll, and was afterwards often referred to as "Colonel".
He was re-elected clerk in 1821 without opposition, and continued to serve until 1822.
In June 1820, he was admitted to the Tennessee bar, and his first case was to defend his father against a public fighting charge; he secured his release for a one-dollar fine.
Samuel became a county judge, and the guests at his home included Andrew Jackson, who had already served as a judge and in Congress.
Polk suffered from frail health as a child, a particular disadvantage in a frontier society.