This Regiment, known as the "Eagle Regiment" was organized 4 September 1861, with a numerical strength of 973. It was mustered into the US service on 13 September and left the state 12 October for the lower Mississippi.

It took part in the actions at Cloutierville and Greenville, Kentucky;

New Madrid/Island 10, Missouri;

Atchafalaya River, Haynes Bluff, Corinth, Vicksburg, and Iuka, Mississippi;

Henderson's Hill, Richmond, Pleasant Hill, and Bayou Lamourie, Louisiana,

Lake Chicot, Arkansas;

Farmington, Jackson, , and Nashville, Tennessee.

The General commanding at Farmington, in general orders, said, "The Badger State may feel proud to have the honor of being represented by so gallant a regiment as the 8th Wisconsin."

General Sherman highly complimented the Regiment for doing "its whole duty in the camp, on the march and in battle," for "Peculiar courage and gallantry at Jackson and throughout the siege of Vicksburg," and for other services.

The original strength of 973 was augmented to a total enrollment of 1,643. Losses by death 255, missing 3, desertion 60, transfer 41, discharge 320. It was mustered out at Demopolis, Alabama on 5 September 1865 with 964 men.