In teacher's idealized history classroom, students are abuzz with questions. They are eager to jump into a serious analysis of primary sources. They relish additional opportunities to engage historiographical debates. They are, as teachers like to say, "thinking historically." While there are few easy ways to create these idealized classrooms, the experiences of one Teaching American History (TAH) grant revealed several lessons that might help strengthen the professional development of K-12 teachers. The Wayne Finger Lakes Board of Cooperative Educational Services (BOCES), in collaboration with the State University of New York at Cortland (SUNY Cortland), received a TAH grant in 2004. Unlike most grants funded by the TAH program, this project, called "Crossroads of Change," focused on a particular period of American history and developed an unusual approach to professional development for history teachers. "Crossroads of Change" immersed teachers in the antebellum period by focusing on the history of a single community and its connection to broader national themes. This article discusses the lessons that might guide other professional development programs and historians working with in-service and pre-service history teachers. (Contains 8 notes.)