As of the census , the population was ,,  making it the fourth-most populous county in Kentucky. Its county seat is Burlington. Native Americans had once inhabited a large late historic village in Petersburg that contained "at least two periods of habitation dating to A. In an unknown Frenchman sketched an area on his chart at what is now Big Bone Lick State Park with a note that it was "where they found the bones of an elephant. In , year-old John Tanner was captured by Shawnee Indians across from the mouth of the Great Miami River , while his Presbyterian minister father, brother, and their slaves were planting corn.