American art has been essential to The Phillips Collection since its founding by Duncan Phillips in 1921. Phillips's collecting interests were decidedly against the grain: he acquired the work of living American artists, especially those outside the mainstream, when it was unpopular to do so and promoted diversity, as seen in works by self-taught artists, artists of color, and naturalized Americans, resulting in a rich assembly of independent-minded artists, including Milton Avery, Stuart Davis, Arthur Dove, and Georgia O'Keeffe. The Phillips Collection's superb collection of American...