The Dynabook research project was a collaborative effort aimed at developing and evaluating a new interactive Web-based resource for use in teacher education to improve how teachers learn to teach middle-school mathematics. This paper describes the outcomes of research during a three-year project to develop and evaluate the effectiveness of the "Dynabook." The purpose of this mixed methods study was to understand how special education college faculty used the proportional Dynabook and how it affected the learning of teacher candidates in their courses, as it was being designed and modified over a period of three years. In the results, faculty note an improvement in the credential candidates' skills in solving proportional problems and answering pedagogical content knowledge questions, and in their mathematical thinking as measured in complexity of classroom discussions. The candidates also reported feeling more confident in their teaching of proportional reasoning, their implementation of UDL, and understanding of TPACK.