Thomas Mills was born on 29 September 1760, in Long Island, N.Y. He moved to South Carolina with his father and older brother and signed up with Lt. Col. Francis Marion during the Revolutionary War. Mills was only 12 or 13 years old at the time. He served with the 2nd South Carolina Regiment and Marion's group, the Swamp Fox Soldiers, from 1776 to 1779. He later traveled to Tennessee, Kentucky, and Ohio where he was a scout and Indian fighter. He met Daniel Boone and knew Simon Kenton well. In 1786, Mills was among several families who petitioned the Commonwealth of Virginia to establish the towns of Washington and Limestone, later known as Maysville. He served in the Corn Stalk Militia between 1791 and 1799 and fought in the War of 1812.