ARTstor (http://www.artstor.org) is a digital library consisting of images in the areas of art, architecture, the humanities and social sciences, along with a set of tools to support use of those images in research and pedagogy. Originally conceived as a project of the Andrew W. Mellon Foundation in 2001, ARTstor became an independent not-for-profit organization in January 2004 and launched the digital library in July of that year. ARTstor works closely with both providers and users of content from educational and cultural institutions around the world in creating a resource that meets the needs of the scholarly, educational and cultural communities. At present, the ARTstor Digital Library contains over 420,000 digital images and descriptive data; software to enable active use of the images in the digital library; and tools that allow users to access and use personal and/or institutional images along with ARTstor content for scholarship and teaching.