Smith County is a county located in the U.S. state of Tennessee. As of the 2010 census, the population was 19,166. Its county seat is Carthage. The county was created in 1799 and is named for Daniel Smith, a Revolutionary War veteran who made the first map of Tennessee and served as a United States senator.Smith County is part of the Nashville-Davidson–Murfreesboro–Franklin, TN Metropolitan Statistical Area.