Marion Township, Charlevoix County, MI is undergoing a transition from an agricultural to a rural residential township. At present, the Township relies entirely upon groundwater as its drinking water supply. An analysis was done to describe the groundwater resource and determine the vulnerability of the resource to surface-derived contaminants. Using CMAP, a personal computer (PC) based geographical information system (GIS) was utilized to obtain a better understanding of the subsurface geology. For Marion Township, groundwater is found in both glacial drift and bedrock aquifers; however, these aquifers appear to be connected hydraulically. Recharge is occurring in the topographic highs of the Township, and discharge is occurring in surface water drainageways. Several potential sources of contamination exist in the Township, with some located in groundwater recharge areas. With this information Marion Township can plan for future development while protecting its groundwater resource.