United States Penitentiary, Leavenworth, Kansas
Carbon Copy for the Files
March 5, 1915
Mr. James A. Refferty,
Bureau of Investigation,
N. Y. City,
In reply to your letter of the 3d instant regarding the correspondence of William B. Schwartz while in this institution, I beg to advise that he received no communications from Julius Hochfelder. On June 18, 1906, however Schwartz received a letter from his brother H. A. Schwartz, Loudenville, Ohio. This may possibly be the H. Swarts you have reference to.
Letter from Warden, R. W. McClaughry, to Jas. A. Rafferty, Chief of Bureau of Investigations, 5 March 1915, William B. Schwartz, Prisoner no. 5476; Inmate Case Files, U. S. Penitentiary, Leavenworth, Kansas, 1895-1931, Record Group 129; National Archives at Kansas City, Missouri.
I guess it makes sense that they kept careful records of letters sent and received.