County boundaries in much of the US are like state boundaries: people drew a bunch of straight lines through a map, with only the slightest regard for natural b

County boundaries in much of the US are like state boundaries: people drew a bunch of straight lines through a map, with only the slightest regard for natural barriers, to create areas of pleasing size. It is quite common to have large population centers crossing county boundaries, or have natural barriers in the middle of a county with population centers on either side.