This article introduces the geographic information systems (GIS) in-service teacher training, focusing on the intersection of technological, pedagogical, and content knowledge (TPACK) for successful implementation of GIS in the classroom. Eleven social studies teachers in Georgia learned GIS technologies, inquiry-based learning, and social studies so that they could create technology-enhanced and inquiry-based lessons using GIS technologies. This article reports participating teachers' opinions and attitudes of the TPACK-based GIS training. It also reports useful pedagogical methods of introducing GIS technologies to students and additional support for teachers to help them use GIS in their classrooms more often.