Caroll County has an area of 458 square miles, was formed in 1842 from Grayson, and was named for Charles Caroll of Carrollton, a signer of the Declaration of Independence; the New River runs through the county. Floyd County has an area of 376 square miles, was formed in 1831 from Montgomery and later added to from Franklin, was named for John Floyd, governor of Virginia from 1830 to 1834, and contains Buffalo Knob.