The primary type of Civil War record is the service record. This record tells you exactly what your Civil War ancestor did during his service in either the Union or the Confederacy. The records will start with when and, most importantly, where your ancestor enlisted to be in the military for the war.
The when is interesting, because you will know if your ancestor jumped in at the beginning in the war, sometime in the middle, or at the end of it. The when may depend on age, as your ancestor may have had to wait until he was of age to join. It may also had to have to do with his family situation, and when he was able to take time away from them to go into military training and travel to engage in battles with the other side.
The where of the record is usually fascinating to genealogists, as it will give you proof of the area in which your ancestor lived at that time. Either he will have enlisted in his city or town of residence, or in the closest city or town that had a place where one could enlist. Either way, you will get an idea of his geographic area of residence if you did not already know it.
Other information you will find in your ancestor’s service record includes payments received (the promised pay for enlisting in the military, as well as additional allotments for food, clothing, and other special needs while your ancestor was in service), engagements in which your ancestor fought, engagements at which your ancestor’s regiment fought but your ancestor was absent (either due to illness, injury, or an approved or unapproved leave), illnesses and/or injuries your ancestor experienced while in the military, any disciplinary records or records of special commendations for bravery or meritorious service, whether your ancestor was killed during his service (and in what manner) or if he died of an illness or injury during the service (and on what date and in what place), the date he was released from his enlistment (if he survived his enlistment in the first place), and where he was when his attachment to the military was terminated.
You will also find other interesting details such as his age at enlistment, his birthplace, his marital status, and whether he had to take an oath of allegiance to the United States (which he would have if he’d been in the Confederacy) after being released from military service, and on what date he took it.
Military service records for the Civil War are kept in envelopes with your ancestor’s regiment name and number on them. This information is also useful to search, as you can look up information on that regiment, and find out more about what your ancestor may have done while serving in the Civil War. You might even find him in a regimental photograph.
Many of these records are online on Fold3 and Ancestry.com in digitized format. You can also find them for both the Union and Confederacy at the National Archives.