Roads are usually named sequentially, although the letter designation may stand for the initials of a road, a geographical feature, a political division (such as CTH-KR along the Kenosha–Racine county line), or in honor of a person.

[1][2] Two county highways running concurrently on the same roadway often take on both letters on that portion; for instance two highways designated CTH-J and CTH-L would take the designation CTH-JL on a certain route before their divergence down the road, returning to their individual route designations thereafter.

Usually the letter designation remains the same when the route is a former state highway that has been decommissioned and turned over to county control.

There are no east–west or north–south pattern restrictions on which letters can be used for a road, and they can be looped around counties and metropolitan areas.

County highways can also run concurrently with state and U.S.