The E911 is a computer-based system that automatically links the dialer's telephone number to its associated civic address, which is then forwarded to the emergency dispatcher, all within seconds. In order for an E911 system to operate properly, the municipal addressing database must be in place and free of errors as much as possible. Although this article's instruction for developing and maintaining an addressing system compatible with an E911 is intended for those jurisdictions that already have an E911 system in place, it can be used as a preceptor tool for those areas preparing to start E911 service. The article advises that an ideal municipal addressing system must provide a physical street address to each land parcel, lot, business, commonplace, and residence in the system's response area. The addressing system must provide the means by which police, fire, and emergency medical services can find every location in the respective county or city at all times of the day and in all weather conditions. This article provides detailed instructions for street signage and address posting, a uniformed numbering system, street naming, and penalties and enforcement. The latter topic refers to a property owner's mandated responsibility to post his address or numbers.