Comprised primarily of letters with Walter Arensberg regarding Southard's poetry and Arensberg's research into the cryptography of Dante. Also includes a handful of personal letters with Southard's niece Pauline who he visited often when in New York City, as well as copies of letters between Southard and Conrad Christian Arensberg. Some letters are on Georgia State Sanitarium letterhead where Southard was a patient in the Fall of 1919.