The Indiana Geological Survey (IGS) has created an Internet map server (IMS) for Marion County in central Indiana. The site provides detailed geologic information needed to address environmental issues, resource management issues, and land-use conflicts related to a growing population. Marion County is the location of Indianapolis, the state capital and largest city in Indiana. The IGS anticipates that the Web site will be widely used by the general public, industry, and government entities concerned about the geology, groundwater, and other natural resources. The Marion County Web site links an IMS and database to provide a portal to the IGS's enterprise geodatabases, which allow users to efficiently create, manage, update, and distribute maps and data. The IMS site retrieves maps of bedrock and surficial geology completed during earlier IGS mapping projects. Hydrogeology, infrastructure, and imagery map layers are also included. Database information includes lithologic information compiled from water-well records stored in the Indiana Department of Natural Resources, Division of Water archives, natural gamma-ray geophysical log data, stratigraphic test hole data, and petroleum well-record data from the IGS Petroleum Database Management System. More recently, the following products have been prepared: (1) illustrated Web pages discussing the surficial geology, bedrock geology, bedrock topography, and hydrogeologic framework; (2) illustrated Web pages discussing digital elevation model terrain, gamma-ray log, iLITH, and clay thickness data sets; (3) online glossary; and (4) metadata for the map layers. The development of the Web site was funded by the IGS and the Great Lakes Geologic Mapping Coalition.