Beginning in the 1890s, the War Department created the Compiled Military Service Record (CMSR) to document the military service of Volunteer soldiers. Transcribed from original muster and pay rolls, regimental returns, descriptive books, hospital rolls, and other records, the CMSRs were intended to permit more rapid and efficient checking of military and medical records in connection with claims for pensions and other veterans’ benefits.
The War Department initially created CMSRs for Union veterans of the Civil War and later expanded the records to include state Volunteers from other conflicts. As a result, the National Archives now holds CMSRs for Volunteer soldiers from the Revolutionary War through the Philippine Insurrection. Link to NARA