(b New Castle, Ind., 13 Sept. 1928).
American painter, sculptor, and graphic artist. His original name was Robert Clark, but he adopted the name of his native state as his own. He is regarded as one of the leading American Pop artists, and although he has done some figurative paintings he is best known for pictures involving geometric shapes emblazoned with lettering and signs. His vivid colours often create effects of visual ambiguity reminiscent of those of Op art.