Funded by the National Center for Research in Geography Education, this study investigated the nature of the knowledge needed for geography teaching. Informed by existing research about science and mathematics teachers’ pedagogical content knowledge (PCK), the research group developed a conceptual model of the knowledge base for geography teaching, identifying six key components: (a) orientations toward teaching geography, (b) knowledge of geography curricula, (c) knowledge of students’ understanding of geography and responses to geography learning, (d) knowledge of instructional strategies appropriate to learning geography, (e) knowledge of assessment of geography learning, and (f) knowledge of educational contexts. The conceptual model was refined and revised according to the results of case studies of four expert geography teachers. Data analyzed included classroom observations, teacher interviews, geography lesson video-recordings, teachers’ lesson plans and reflections, and student work samples. The resulting preliminary model (GeoKBT) is offered to the geography education community to inform both geography teacher education and further research on geography-related pedagogical knowledge.