The Eighteenth Wisconsin Infantry Regiment was organized at Milwaukee, Wisconsin, and mustered into the service of the United States on March 15th, 1862. It left the state March 30, and disembarked at Pittsburg Landing, TN, April 5, 1862, at once moving up to the front. The battle opened early next morning and the Eighteenth shared the varying fortunes of the brigade to which it had been assigned during the battle of Shiloh, April 6-7, 1862. After the battle the Eighteenth participated in the advance on and siege of Corinth, MS, April 29 to June 10, 1862, and the battle of Corinth, October 3-4, 1862.
Thereafter it engaged in various expeditions preceding the assembling of the Union forces at Grand Junction in November preparatory to the advance on Vicksburg. After the change of plans, the Eighteenth marched to Memphis, from which it embarked down the Mississippi reaching Young's Point, LA on January 25, 1863. Later the men were employed on the canal which was dug to enable Grant's army to pass below Vicksburg. Crossing the Mississippi River below Vicksburg the regiment reported to General McPherson at Raymond, MS on May 13, and moving with the union forces took part in the battle of Jackson, MS, May 14, which was soon thereafter followed by the battle at Champion's Hill, May 16, and Black River Bridge, May 17, 1863. Soon thereafter it took its position in the trenches encompassing Vicksburg, where it remained until the surrender. (Siege of Vicksburg, May 19-July 4, 1863). After the surrender the Eighteenth remained in the vicinity of Vicksburg doing guard and fatigue duty until September.
Thereupon it was transferred to Memphis, TN and thence to Corinth, MS. Here the Union forces were assembled to assist in the relief of Chattanooga. The Eighteenth as a part of the Fifteenth Army Corps, after a march of about two hundred fifty miles with these forces under General Sherman, reached Chattanooga, and on November 24th crossed the Tennessee river and participated in the attack on Missionary Ridge November 25. Thereafter the Eighteenth was assigned to the work of protecting the lines of communication. Assigned at times to Huntsville, Stevenson, AL, Chattanooga, TN and Allatoona, GA and south of Chattanooga on the road to Atlanta, with headquarters at Allatoona. In the attack on that place October 5, 1864, the Eighteenth was actively engaged in the famous defense. A portion of the regiment accompanied General Sherman on the Savannah and Carolina Campaigns. That portion remaining in Tennessee joined the detachment accompanying General Sherman at Goldsboro, NC, the latter part of March 1865.
After the surrender of the Confederates under General Johnston April 26, 1865, the Eighteenth participated in the Grand Review at Washington, D.C. and was transferred to Louisville, KY as a part of the Provisional Division, where the regiment remained until mustered out July 18. It returned to Madison, WI and was disbanded July 29, 1865.