Cultural heritage institutions store and digitize large amounts of multimedia data inside archives to make archival records findable by archivists, scientists, and general public. Cataloging standards vary from archive to archive and, therefore, the sharing and use of this data are limited. To solve this issue, linked open data (LOD) is rising as an essential paradigm to open and provide access to the archival resources. Archives which are opened to the world knowledge benefit from external connections by enabling the application of automated approaches to process archival records, helping all stakeholders to gain valuable insights. In this paper, we present the Archive Dynamics Ontology (ArDO) - an ontology designed for describing the hierarchical nature of archival multimedia data, as well as its application on the example of archival resources about the Weimar Republic. Furthermore, ArDO semantically organizes multimedia archival resources in form of texts, images, audios, and videos by representing the dynamics related to their classification over time. ArDO tracks the changes of a specific hierarchical classification schema referred to as systematics adopted to organize archival resources under semantically defined keywords.