Carroll County is a United States county located in the southwestern part of the Commonwealth of Virginia. Roughly one fifth of the county lies in the Virginia Piedmont region, while the rest is part of the Appalachian Mountains. The county seat and largest town is Hillsville. The county was established in 1842 from part of Grayson County, and was officially named in honor of Charles Carroll, a signer of the Declaration of Independence. The borders of Carroll County were later expanded by including land from Patrick County.