Epistemological and ontological perspectives on design have changed dramatically in the past century, and yet library classification systems have not been updated accordingly. This article examines where design is—and is not—classified in the two dominant library classification systems in America, Dewey Decimal Classification and Library of Congress Classification, and what this expresses regarding design as a domain. This article demonstrates how such classification relegates design theory as subordinate to the product and can lead to information siloes, diminish creativity, and interdisciplinary study.