County routes in Sullivan County, New York, are maintained by the Sullivan County highway department and signed with the Manual on Uniform Traffic Control Devices-standard yellow-on-blue pentagon route marker. The county highway system comprises roughly 140 routes arranged across the county in groups of nine. For the most part, state routes in Sullivan County are county-maintained and co-signed with county routes. However, the converse is not true; that is, not all county routes overlap state routes for their entire length. Typically, each series consists of county routes along a single roadway, often overlapping with state highways in the process. The lowest numbered route in the system is County Route 11 (CR 11); the highest is CR 183C.