The plaza is one of the most important elements of the built environment for bringing people together in the Pueblo World of the US Southwest. Yet, the myriad ways in which plazas were designed and used vary greatly through time. Although plazas have been significant components of Ancestral Pueblo site layouts for hundreds of years, nearly every research study has been based on the enclosed plazas of the Pueblo IV period. In this article, we evaluate variation in 861 plazas from the Pueblo World dating from AD 800 to 1550. Our analysis of settlement size, plaza area, and degrees of plaza accessibility demonstrates that the spacious plazas emblematic of the Pueblo IV period were built to accommodate more people than the resident population, suggesting the origins of the feast-day-type ceremonialism seen in contemporary Pueblo communities. Our analysis suggests that this is a relatively recent phenomenon, because plazas in earlier Chaco great house communities were built to be more exclusionary, and thus activities held within them were more restricted.