Hardeman was a captain in William Bean’s Company of Watauga Riflemen at the battle of King’s Mountain.
In 1782 and 1783, Hardeman served as a captain under Col. Sevier in the battles against the Cherokee Towns. After the Revolutionary War his service to the new nation continued and in 1788, he served in both the North Carolina House of Commons and North Carolina Convention to ratify the Constitution. He served in the legislature of The Territory south of the River Ohio in 1795 and in Tennessee’s Constitutional Convention of 1796. Hardeman was a Senator in the Tennessee Second General Assembly in 1797-99, representing Davidson County. His first wife, Mary Hardeman, died in 1798 and he ended his public service. Hardeman married his widowed sister-in-law Susanna Perkins Marr in 1799. In 1816 upon the death of his second wife, he moved to Howard County, Missouri. His son John and family joined him soon after. Letters from his political allies in Tennessee urged him to become involved in the drafting of the Missouri to take advantage of his experiences in constructing the Tennessee State Constitution. He lived with his son until John’s death in 1829, when he felt a burden to the family and moved back to Tennessee. Hardeman died in Williamson County, Tennessee on June 3, 1833. The legacy of civil service of Thomas Hardeman was carried on by several of his descendants, with sons serving as county clerks, serving in the War of 1812, and two sons, Bailey and Thomas Jones Hardeman, participating in the first government of the Republic of Texas. His grandson Peter Hardeman Burnett was the first Governor of California. Thomas Hardeman was a patriot of the backcountry, a states’ rights supporter who helped build a nation he fought to create.