He received AB magna cum laude at Princeton University in 1954. Then he got Master of Arts at Harvard University in 1963, and Doctor of Philosophy there in 1971.
He worked as Curator of Nineteenth Century Art at the Los Angeles County Museum (1971-74) before becoming Chief Curator of the Hirshhorn Museum and Sculpture Garden (1973-86). From 1986-93 he made a memorable Director of the Ackland Art Museum at the University of North Carolina, Chapel Hill. (In 2015, the University would award him an Honorary Doctorate of Fine Arts.) Millard securely tied the Ackland’s mission to university teaching. He invited students to museum events and began a steady public outreach that included local children. Millard described the seven years heading the Ackland as his happiest.