Are you trying to discover if your relatives served in the Civil War? First, check the index on the Civil War Soldiers and Sailors website sponsored by the National Park Service. This index, compiled from the general index cards of Compiled Military Service Records, lists more than 6 million names of Union and Confederate servicemen. Why 6 million names when roughly 3 million served? Because separate CMSRs were created if the soldier served in more than one unit or if his name was spelled differently on different records. Each CMSR merits a separate entry in the database.
Then, surf to the Civil War Collection on Ancestry to search various Civil War related databases including the General Index to Pension Files. More than 2 million pension applications are indexed in this database.
You can also spot veterans on census records. The 1890 Special Veteran’s census schedule still exists for states beginning with the letters K through W. Actually, only half of the Kentucky records are still available. For your long-lived veterans, check the 1910 census. Look under column 30. Here you might find a check, indicating the person served in the Civil War, or a scribbled “ua” for Union army or “ca” for Confederate army. For really long-lived veterans, scan the 1930 census. Columns 30 and 31 posed questions about military service. You’ll see “Civ” written for Civil War veterans.
-Taken from ancestry.com