The 166th Ohio Infantry Regiment lost 39 enlisted men to disease during the Civil War.
|Organized at Camp Cleveland, Ohio|
|May 13||960 men were mustered in under Colonel Harrison G. Blake|
|May 15||Left State for Washington, D.C. Attached to 2nd Brigade, DeRussy’s Division, 22nd Army Corps.|
|July||Assigned to duty as garrison at Forts Richardson, Barnard, Reynolds, Ward and Worth (Headquarters at Fort Richardson), Defenses of Washington south of the Potomac. Attached to 3rd Brigade, DeRussy’s Division, 22nd Army Corps.|
|July 11-12||Repulse of Early’s attack on Washington|
|September 9||Mustered out|