Data were compiled via questionnaire survey. The survey gathered information on community demographic characteristics, telephone companies and equipment, Public Safety Answering Points (PSAP), systems management, financing, and related information. Questionnaires were mailed to the PSAP directors of 762 operating 911 systems in 1979; followup telephone calls were also used, and over 400 responses were received. The directory's information is organized alphabetically by State. Each State's section has three parts: 911 system descriptions, a list of survey nonrespondents, and a list of 911 systems not contacted. For each operating system, the community characteristics, historical background, telephone system, and PSAP administration and operations are described. The system's legal and fiscal aspects are also described. Brief comments summarize the system's problem areas. The name, address, and telephone number of the PSAP director are also given. Nonrespondents' names, addresses, and telephone numbers are listed alphabetically by city. The directory is cross-referenced according to the size of the population served, the type of agency at which the PSAP is located, and the number of political jurisdictions served.