Nearly fifty years after the incorporation of the International Society for Knowledge Organization and the introduction of its formal scientific journal Knowledge Organization, a comprehensive encyclopedia of the domain appeared. The practice of domain analysis for knowledge organization, twenty years after its introduction as a core methodology, has created the largest corpus of theoretical knowledge in the domain analysis of knowledge organization itself. A substantial body of research data, therefore, is available in the corpus of articles and conference papers reporting on the epistemological and ontological pillars of the science of knowledge organization. This paper is a report on the evolution of a formal taxonomy of knowledge organization, which is a product of an exhaustive meta-analysis of the KO domain. Our team compiled the corpus of twenty-nine formal published analyses together with key formative historical documents. We then analyzed the corpus thematically, bibliographically, and using co-word analysis to extract key concepts and the underlying faceted conceptual infrastructure. The taxonomy itself is faceted and is linked where possible to published definitions in the KO literature and as well as to the online ISKO Encyclopedia of Knowledge Organization. A dynamic project, the taxonomy will be maintained as linked open data and will grow as emergent research contributes new concepts or generates new facets.