12th Regiment, Ohio Infantry (3 months, 1861)
The 12th Regiment, Ohio Infantry (3 months, 1861) mustered in April and May, 1861 at Camp Jackson, Columbus, Ohio. They were mustered out July 25, 1861 at Camp Dennison, Ohio. 
For more information on the history of this unit, see:
- Larry Stevens' Ohio in the Civil War, 12th Ohio Infantry
- Ohio in the Civil War, 12th Regiment Ohio Volunteer Infantry (Three Months Service), (accessed 26 October 2016)
Companies in this Regiment with the Counties of Origin
Men often enlisted in a company recruited in the counties where they lived though not always. After many battles, companies might be combined because so many men were killed or wounded. However if you are unsure which company your ancestor was in, try the company recruited in his county first.
County listing from Steve Ward's Buckeyes All, Part II Revised, as given on Larry Stevens' Ohio in the Civil War web page, 12th Ohio Infantry.
- 12th Ohio Regiment Infantry (3 months), Civil War Index, which includes history, battles, and roster with name, rank, age, date entered service, period of service and remarks.
- Beginning United States Civil War Research gives steps for finding information about a Civil War soldier. It covers the major records that should be used. Additional records are described in ‘Ohio in the Civil War’ and ‘United States Civil War, 1861 to 1865’ (see below).
- National Park Service, The Civil War Soldiers and Sailors System, is searchable by soldier's name and state. It contains basic facts about soldiers on both sides of the Civil War, a list of regiments, descriptions of significant battles, sources of the information, and suggestions for where to find additional information.
- Ohio in the Civil War describes many Confederate and Union sources, specifically for Ohio, and how to find them.. These include compiled service records, pension records, rosters, cemetery records, Internet databases, published books, etc.
- United States Civil War, 1861 to 1865 describes and explains United States and Confederate States records, rather than state records, and how to find them. These include veterans’ censuses, compiled service records, pension records, rosters, cemetery records, Internet databases, published books, etc.
- National Park Service, The Civil War Soldiers and Sailors System, (accessed 6 December 2010).