Montgomery County, Maryland, Department of Public Works & Transportation, is building an expert system for site selection using ArcView GIS/SDE. All the critical factors and processes in planning to construct a facility will be stored in a database. This database (knowledge base) will be used with GIS to identify potential sites for constructing different facilities. Like geocoding, the system will identify potential sites and assign scores based on information from the knowledge database. The users will be able to view, relax, or intensify the thresholds and ranking by importance used by the system.