Marshall County is a county located in the U.S. state of Tennessee. As of the 2010 census, the population was 30,617. Its county seat is Lewisburg.Marshall County comprises the Lewisburg, TN Micropolitan Statistical Area, which is also included in the Nashville-Davidson-Murfreseboro, TN Combined Statistical Area.Marshall County is the home of the Tennessee Walking Horse Breeders' and Exhibitors' Association. Another native of Marshall County is the fainting goat.