Abstract: Colonel Franklin T. Matthias (1908-1993) was commanding officer and area engineer of the Hanford Engineer Works of the Manhattan Engineer District. 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.