Military records can be a rich source of details for your family history. They convey basic information such as name, residence, age, and may also provide a physical description. They also provide details of military service that can enrich your understanding of their lives -- dates mustered in and out of service, the unit served in, a record of injuries sustained, and so on. And if you're lucky enough to find a pension file, it may include not only information about military service but records of important family events such as birth, marriage and death certificates, letters, and perhaps even photographs.
Revolutionary War Resources:
War of 1812:
Civil War:
Civil War Soldiers & Sailors Database