The colletion contains Curia files, correspondence, military records, photographs, newspaper clippings, and ephemera. Of particular interest to researchers are correspondence and documents to / from individual prisoners in the Alcatraz Federal Penitentiary whom Father Clark served as prison chaplain. These men include: John Rosselli, Alvin Karpis, John Paul Chase, and Al Capone among others. Father Clark taught painting to inmates, including John Paul Chase. Their work was exhibited in Union Square, San Francisco in the late 1940s.

Joseph Mahoney Clark was born in Deming, New Mexico, 10 June 1900. After graduating from Loyola High School in Los Angeles in 1918, he trained in the Army Corps of Engineers. He entered the Society of Jesus in the California Province in 1919. After seven years of formation and study he taught physics at St. Ignatius College and High School in San Francisco and then at Brophy College Preparatory in Phoenix. He studied theology at Weston College in Massachusetts where he was ordained in 1932. Father Clark was most noted for his work as a hospital chaplain in San Francisco General Hospital and prison chaplain at Alcatraz, 1935-1942 and again 1946-1952. In World War II he served as a military chaplain in the 59th Evacuation Hospital, 1942-1944, and the 35th Field Hospital, 1944-1945, in North Africa and Italy. From 1957 to 1964 he was pastor of St. Henry's Church in Brigham City, Utah. His final service as a chaplain was spent as St. Joseph's Hospital in Phoenix, 1964-1971. He died in the Regis Infirmary at the Sacred Heart Jesuit Center in Los Gatos, 20 February 1980.

2.0 Linear feet