ROBERT S. SCURLOCK, Marian Anderson’s Easter concert at the Lincoln Memorial, April 9, 1939 (negative). | Scurlock Studio Records, Archives Center, National Museum of American History, Smithsonian Institution   FROM THE STEPS of the Lincoln Memorial in Washington, D.C., Marian Anderson (1897-1993) gave a memorable concert on April 9, 1939. The contralto singer opened with...