Muster roll

To muster meant to assemble a unit and account for each man. The resulting roll named the officers and men, their rank and the dates they joined or left, with remarks on sickness, desertion, death or discharge. Many rolls also served as pay rolls.

For Volunteer soldiers, War Department clerks later copied each man's entries from the rolls onto cards, which became his compiled military service record. NARA advises using those cards first, because many original rolls are too fragile to handle. Regular Army rolls are arranged by regiment, then company, then date.