79th Regiment, Ohio Infantry
The 66th Regiment, Ohio Infantry mustered in December 17, 1861 at Camp McArthur, Urbana, Ohio. They were mustered out July 15, 1865 at Louisville, Kentucky. 
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.
National Park Service, The Civil War Soldiers and Sailors System, (accessed 6 December 2010).
- National Park Service, The Civil War Soldiers and Sailors System, (accessed 6 December 2010).