20210714 13260200 1.0 TRUE ESN Boundaries This dataset depicts the Emergency Service Number (ESN) Boundaries for Mono County, CA. The ESN (Emergency Service Number) is a code assigned to each line of the MSAG. It tells the telecommunicator which fire protection, law enforcement and emergency medical service to send to any given address in the county. The ESN is a core element in theEnhanced 9-1-1 system. County of Mono, CA IT Department / GIS Division PO Box 7657 437 Old Mammoth Road, Suite 288 Mammoth Lakes, CA 93546 (760) 932-5500 gis@mono.ca.gov http://gis.mono.ca.gov