Provenance is the history of ownership of an object from the time it was created until the present day. It includes information about former owners, dates of transfer, and the types of transactions that led an object to change hands from one owner to another. From its inception, the National Gallery of Art has conducted extensive research into the provenance of the works in its collection as part of its commitment to art-historical scholarship. Provenance research can reveal much about a work, even beyond the recital of names and dates, from confirming authorship to how it was valued and displayed. In the last decades the Gallery has paid particular attention to the location and ownership of art during the World War II era, in the spirit of the Washington Conference Principles and guidelines from the Association of Art Museum Directors (AAMD) and American Alliance of Museums (AAM), becoming an early leader in this area.