Good news: If you know your ancestor's Civil War unit, use this form to determine the county in Tennessee from which that unit was raised.
Bad news: Men often went across county lines to enlist, so you should also look at all adjoining counties in your search for records.
Good news: If you know the county, use this form to determine the units raised in that county.
Bad news: Muster rolls often indicated the county in which a unit was mustered into service, but not the counties from which those men came. Consequently, your ancestor may not have enlisted in one of these units.
Please also be aware that, as units were decimated in battle, the survivors were often consolidated with other fragmented units, and the units renamed. Because of this, and the paucity of battlefield records, the unit a man enlisted in, and the unit which he or his widow claimed on a pension record, were often not the same.
Long names (commander's names) are often significant, as there are duplicate regiments with the same number, raised in different counties. Also notice that, while some counties were not formed until after the war, there are still units often attributed to the area that became that county.