He fought in the American Civil War for the Confederate States of America, and was wounded at the Battle of Gettysburg.

Returning to North Carolina after the war, Polk founded the town of Polkton, incorporated in 1875, where he started a weekly newspaper called The Ansonian.

An agricultural collection he established as Commissioner was the basis for what became the North Carolina Museum of Natural Sciences.

In the late 1880s, Polk rose to nationwide prominence through his leadership of the state and national Farmers' Alliance, which had begun in Texas.

The Populists likely would have nominated Polk for president in 1892 (see 1892 U.S. presidential election), but he died unexpectedly from a hemorrhaging bladder in Washington, D.C., on June 11, 1892.