Collectively, the Archives of American Art constitute the world's largest repository of primary source materials on the history of the visual arts in the United States. Its collections include more than 12 million items dating from 1620 to the present, including the letters, diaries and sketchbooks of artists; the papers of important galleries, collectors and critics; more than half a million photographs of artists and their work; and some 3,000 oral history interviews with artists and art world figures. Of its five regional centers (Boston, MA; Washington D.C.; San Marino, CA; Detroit, MI; and New York City), only New York offers regular exhibitions. These draw on the institution's rich holdings and items on loan from museums, collectors and dealers. Exhibitions have featured such important American artists as Romare Bearden, Chuck Close and Ellsworth Kelly.