Carroll County covers 458 square miles, was formed in 1842 from Grayson, and was named for Charles Carroll of Carrollton, signer of the Declaration of Independence; the New River runs through the county. Floyd County covers 376 square miles, was formed in 1831 from Montgomery and later enlarged from Franklin, was named for John Floyd, Governor of Virginia from 1830 to 1834, and includes Buffalo Knob.