This report is one of a series of reports describing the historical developments and current state of distance education, online learning, and blended learning. with the intent of informing future research and practice in the emerging discipline of digital learning, this tertiary study focuses on the history and state of distance education, and the understanding of the large body of empirical research as captured by secondary studies (i.e., meta-analyses and systematic literature reviews). we conducted an automated search for secondary studies in several online digital libraries, and a manual search through Google Scholar and the ten most relevant academic journals. Our search identified 339 secondary studies in the domains of distance education, online learning, and blended learning. of those, 37 secondary studies on distance education research and practice met the selection criteria for final inclusion in our study. Based on the analysis of these secondary sources, three main themes emerged: i) comparison of distance education and traditional classroom instruction, ii) identification of important factors of distance education delivery, and iii) factors of institutional adoption of distance education. our results indicate that distance education, when properly planned, designed, and supported by the appropriate mix of technology and pedagogy, is equivalent to, or in certain scenarios more effective than, traditional face-to-face classroom instruction. This highlights the importance of instructional design and the active role of institutions play in providing support structures for instructors and learners. The implications for future research and practice are discussed.