In 1890, the War Department began compiling histories of the Union volunteer military organizations serving during the Civil War.  These compiled records for each organization were called "Record of Events" and contained abstracts of the information found on muster-in and muster-out rolls for the units. Starting in 1903, the War Department began to compile abstract histories of the movements and activities of the Confederate units.  The principal sources of data for Confederate organizations were the original muster rolls and returns, as well as the rosters, payrolls, hospital registers, casualty lists, prison registers, parole rolls, and inspection reports.

     Unit Records provide information regarding the stations, movements, activities, organization, composition, strength and losses, and disbandment of the units.  Additionally, there are frequent glimpses into the day-today life of the soldiers.  Location stations, muster-in dates and personnel, distances between location assignments, orders received, enemy engagements, losses sustained, unit nicknames, and terms of service are just some of the many details provided in the unit histories.

     Usually the Union records are more complete than the Confederate records, but many of the Confederate units also include rosters of officers.