This essay contributes to the growing literature on Mexican American Studies in K-12 within the broader field of Ethnic Studies. While most of the literature on the movement for Ethnic Studies within Texas and across the nation mainly focuses on the impact of Ethnic Studies courses on students' academic success, this essay highlights a professional development program for K-12 social studies teachers in the Rio Grande Valley of South Texas entitled "Historias Americanas: Engaging History and Citizenship in the Rio Grande Valley," funded by a federal grant. This essay provides an overview of Historias Americanas, the objectives and structure of the program, and the ways in which the program contributes to the discourse on Mexican American Studies in K-12. It also describes the frameworks that form the crux of the professional development process: place-based education and culturally relevant pedagogical frameworks.