Military Service Records, Awards, and Unit Histories: A Guide to Locating Sources [Updated December 5, 2019] [open pdf - 1004KB]
From the Summary: "This guide provides information on locating military unit histories and individual service records of discharged, retired, and deceased military personnel. It also provides information on locating and replacing military awards and medals. Included is contact information for military history centers, websites for additional sources of research, and a bibliography of other publications, including related CRS [Congressional Research Service] reports."
CRS Report for Congress, RS21282
Congressional Research Service: https://crsreports.congress.gov/