Contaminated unregulated drinking water in rural communities is a continuing health issue, leading many resource users to unknowingly consume water with elevated levels of harmful chemicals. Though geographic information systems (GIS) and Internet technology have been particularly useful for water resource management, to date, there exist few studies that specifically address the development of Internet-based GIS applications to increase user access to unregulated drinking water source information. Informed by an existing user centered development framework for Internet mapping, we created an Internet GIS that visualized groundwater contamination on the Navajo Nation in the southwest United States. We employed a usability focus group, expert review of content and pilot test of a prototype GIS application to gather empirical evidence on effectiveness for informing users of a significant water quality issue. Results suggested that the designed and deployed GIS application was appropriate for the target audience of environmental nongovernmental organization (ENGO) and institution of higher education (IHE) professionals. Usability testing and expert review confirmed the importance of these evaluation measures to ensure a high quality GIS prior to deployment. Use of existing Internet mapping guidelines was found to be insufficient for creating a refined GIS interface appropriate for the target audience. Additionally, we demonstrated that an existing user centered design and evaluation framework could be applied successfully to visualize water quality for unregulated groundwater wells in the rural southwest United States. Suggestions for continued research in the use of Internet GIS to inform rural residents about drinking water quality are provided. © 2014 Elsevier Ltd.