These are Colonel Matthias's personal papers documenting his work on the Manhattan Project. They include original declassified documents from Hanford and a variety of newspaper clippings and magazine articles collected by Matthias between the time he left Hanford to his death, reflecting his continuing interest in the Manhattan Project and nuclear power.

The bulk of the papers are newspaper clippings, many generated by Matthias's need to maintain secrecy during the war and then provide information once the existence of the bomb was announced. There are, however, a number of original documents and photographs covering the construction at Hanford and Richland, including organization charts, lists of army personnel, site plans, texts of radio interviews and speeches, and internal publications dealing with employee morale, security and safety. Of note are a booklet of employee cartoons critical of the spartan living conditions at Hanford, a signed booklet of song parodies put together by the WACs assigned to Hanford, and a DuPont manual, "The Hanford Business Girl." The is also a copy of a large presentation book on the Hanford project issued to senior staff, and the relevant portion of the Corps of Engineers' history of the Manhattan Project.

The papers also contain a small amount of information on the Clinton Engineer Works at Oak Ridge, a copy of the first public report on the results of the atomic bombings of Hiroshima and Nagasaki, and a history of the Sandia Corporation, which manufactured and tested atomic weapons under contract between 1949 and 1980.