This article describes the findings of a study involving a professional development program that prepared middle school teachers to integrate content on the earliest eras of world history and world geography. In particular, this study focused on participants' (n = 37) use of geographic resources to integrate geography and history and to encourage spatial thinking. Teachers were enthusiastic about all of the resources and used them to integrate geography and history content. Thus, this study found that teachers will adopt relevant and accessible materials if they are trained to use them. The "Atlas of World History" was the most widely adopted resource; the mapping software StrataLogica was more effective at promoting spatial thinking, but the teachers found it to be less accessible and therefore did not use it as often.