In the mid-1980s, William S. Arnett, a writer, curator, entrepreneur, Georgia native, and collector of African art, turned his attention closer to home—the efforts of self-taught African-American artists of the rural South. Mr. Arnett became a passionate collector and advocate of this work, characterizing it as the visual counterpart of jazz, a uniquely American, improvisational art form forged from African roots and the troubled history of American black experience: slavery, the Civil War, emancipation, reconstruction, Jim Crow segregation, lynchings, the civil-rights movement. In 2010, Mr. Arnett created the Souls Grown Deep Foundation—the name comes from a Langston Hughes poem—which, among other things, has supported artists in the collection, organized exhibitions, and published handsome volumes. Recently, the foundation has made donations to museums across the U.S., including, in 2014, 57 works to the Metropolitan Museum of Art.