Art historian, curator and collector of medieval and 17th-century European art. Heil left Germany to become curator of European art at the Detroit Institute of Art in1926. In 1933 he was appointed dual director of the California Palace of the Legion of Honor and the M.H de Young Memorial Museum in San Francisco (today merged as the Fine Arts Museums of San Francisco). There, in 1934 he hired the German expatriate Elizabeth Moses to be the curator of the arts and crafts at the de Young. With the United States in the height of the Depression, the same year he also took on the job of the Region 15 Director (Northern California, Nevada, and Utah) of the Public Works of Art Project (PWAP) until 1936. In 1939 he was named director of the de Young, solely, which he served until 1961.
Heil brought the museum to international recognition through early exhibitions of Max Beckmann (1949),Oskar Kokoschka (1950) and Edvard Munch (1951). Among his personal art collections was a self-portrait by Thomas Gainsborough, today in the British Museum.