After McCarthy's death his papers remained in the possession of his widow. In 1927 they were shipped to Louis B. Wehle in New York for his use in a planned biography of McCarthy. The biography never materialized but the papers remained in Wehle's possession until August 1939 when, on Lucile McCarthy's instructions, the two four-drawer file cabinets and two large wooden packing crates of papers were shipped to the State Historical Society of Wisconsin. This basic collection has been augmented over the years by numerous small donations of papers from McCarthy's daughter, Katherine McCarthy Aumann. The most recent of these gifts came in 1981 and 1982 when Mrs. Aumann sent a group of photographs, clippings, and correspondence of her late father. In 1955 Edward A. Fitzpatrick, author of the biography McCarthy of Wisconsin, donated his research material, and some correspondence from the early 1920s of a McCarthy Memorial Association. The collection also includes photocopies of correspondence between McCarthy and John D. Rockefeller Jr., in addition to a few original letters. It seems likely that the copies came from the Rockefeller family archives, although it is not known how they became part of the Society's collection.
Except for the oversize items in this collection, all of this material is available both in paper form and on microfilm. It was microfilmed in 1982 in a publication project sponsored by the National Historical Records and Publications Commission and most of the narrative above and below is drawn from the published guide to that microfilm publication. The publication project addressed papers of Wisconsin Progressives, individuals who were connected with the University of Wisconsin or the Wisconsin state government and were intellectual leaders of the Progressive era. Other editions in the series are the Richard T. Ely Papers, Charles R. Van Hise Papers, Edward A. Ross Papers, and John R. Commons Papers. All of these individuals had leading roles in the ideological changes which led to the demise of Social Darwinism, the abandonment of laissez faire economics, the democratization of the electoral process, and the assumption by government of a positive role in furthering the cause of reform. Moreover, several of them had a direct hand in the design and implementation of major Progressive era reforms.
A few other papers and records originating with McCarthy can be found in the official records of the Legislative Reference Library (now called Legislative Reference Bureau) and are not part of this microfilm edition. The Bureau's files in the state capitol contain a few miscellaneous McCarthy letters, but it is believed that most correspondence predating 1922, and bill drafting records predating 1927 were destroyed about 1930. The only substantial set of McCarthy era records still maintained by the Bureau are topically organized reference files made up primarily of newspaper clippings.
For the period it was under McCarthy's direction the Legislative Reference Library was a part of the Wisconsin Free Library Commission. Commission records held by the State Historical Society include occasional correspondence and reports of McCarthy which are also not part of this microfilm edition. The Society also holds a microfilm copy of letters between McCarthy and Sir Horace Plunkett obtained from the Plunkett archives in Ireland. Finally, the University of Wisconsin Memorial Library has a collection attributed to McCarthy of mounted newspaper clippings, 1920-1921, on the Irish rebellion (Cutter call number F 426 + ZZ).
