The scalability and accessibility of quality professional development (PD) is an ongoing concern in the teacher education community, yet little research has been conducted on potential solutions. We aimed to address this gap by developing an interactive, virtual PD program that uses intelligent tutoring systems and provides instant feedback to teachers. We then explored the role of this program in developing teachers' content and pedagogical content knowledge of mathematics. We collected data from 60 teachers located across the USA and found that those who completed the program increased their content and pedagogical content knowledge. [This is the online first version of an article published in "Journal of Mathematics Teacher Education."]