Utilizing a full-text 15,926,460-word database of all peer-reviewed articles published in six public relations journals between 2012 and 2022 (N=2,675), we employ a variety of computational methods to investigate the past, present, and future of internal communication in public relations.We first situate internal communication studies in the wider public relations literature, document its growth, identify a set of "internal-communication papers" (N=407), and conduct a comprehensive bibliometric analysis. Next, we investigate the theoretical, empirical, and epistemological origins of internal communication by analyzing all identified internal communication papers' reference lists and providing core readings for the research community.Finally, we compare internal communication papers with non-internal-communication counterparts, quantify literature gaps, and illuminate promising research directions to guide the future of internal communication studies.