Understanding and supporting students' development of graph literacy is important. We studied how aspects of graph literacy might be supported (or hindered) in middle school by analyzing the content in textbooks. Specifically, we conducted a content analysis of tasks involving two-dimensional Cartesian graphs presented in grade 6-8 US textbooks. Three elements were analyzed: the type of activity involved in graphing, the nature of the graph, and the relevant mathematical topic. We first present three illustrative tasks to demonstrate how we made sense of these three elements with graphing tasks. Second, we present the frequency of different types of coordinate system activity, graph activity, and coordinate system types involved in textbook tasks and how they change across grade level and mathematical domain. Our findings reveal varying levels of exposure to different graphing elements students might encounter through textbooks. We discuss implications of our findings on research, teaching, and curriculum development.