The Milwaukee-class monitors were a class of four riverine ironclad monitors built during the American Civil War. Several supported Union forces along the Mississippi River in mid-1864 before participating in the Battle of Mobile Bay in August. Milwaukee struck a torpedo during this time and sank. The surviving three ships were sold in 1874; Chickasaw was converted into a ferry and survived until 1944 when she was scuttled.

The ships' main armament consisted of four smoothbore 11-inch Dahlgren guns mounted in two twin-gun turrets. The fore turret in each ship, except Chickasaw, was designed by Eads, while the aft turret was the standard Ericsson design used in most Union monitors. Unlike the latter, which rested its entire weight on a central spindle that had to be elevated in order for the turret to rotate, Eads' design better distributed its weight because it rested on a number of ball bearings underneath the outer edge of the turret. The structure of the Eads turret extended down to be bottom of the ship and the entire structure rotated. The guns in the Eads turret were mounted on a steam-powered platform that moved up and down, so that the guns could be reloaded below deck, safe from enemy interference. The ability to adjust the level of the turret floor doubled the elevation of the guns to +20° compared to the +10° allowed in an Ericsson turret. Another advantage was that the Eads turret only required a crew of six men, far fewer than the Ericsson design. Each gun weighed approximately 16,000 pounds. They could fire a 136-pound shell up to a range of 3,650 yards.

The cylindrical turrets were protected by eight layers of wrought iron 1-inch plates above the deck. The sides of the hull consisted of three layers of one-inch plates, backed by 15 inches of pine. The deck was heavily cambered to allow headroom for the crew on such a shallow draft. Milwaukee and Winnebago had an additional layer of armor to give them a total of 1.5 inches. The pilothouse, positioned behind and above the fore turret, was protected by 3 inches of armor.

The Milwaukee was laid down on 27 May 1862 at Carondelet, Mo. and commissioned at Mound City, Ill., on 27 August 1864. Milwaukee was 229 feet long and displaced 1,300 long tons. Her crew numbered 138 officers and enlisted men. The engines were designed to reach a top speed of 9 knots (10 mph). Milwaukee carried 156 long tons of coal.

Milwaukee was initially assigned to the Mississippi Squadron upon commissioning but saw no action. On 1 October 1864, Rear Adm. David D. Porter, commanding the Mississippi Squadron, ordered USS Milwaukee to Mobile, Ala., and report to Rear Adm. David G. Farragut for duty with the West Gulf Blockading Squadron. The ship departed Mound City, Illinois on 15 October and arrived at New Orleans, Louisiana 12 days later.

Rear Adm. Farragut’s decisive victory at Mobile Bay on 5 August 1864 had essentially closed that port to the South, but the city still lay in Confederate hands. To defend it, the South heavily mined the shallow water that led to the city, filled it with formidable obstructions and erected batteries to shell any ships that had managed to penetrate the fixed defenses.

New Year’s Day found USS Milwaukee in Mobile Bay ready for action. In the following months, with other light‑draft Union ships, she swept mines, bombarded Confederate works, removed obstructions and transported Army troops.

On 27 March 1865, Milwaukee, together with several other Union ships, sortied upriver in an attempt to cut communications between Spanish Fort and Mobile. The following day she and her sister ship Winnebago steamed up the Blakely River to attack a Confederate transport and forced it to retreat. While returning downriver Milwaukee struck a mine in an area previously swept. She remained afloat forward, which permitted her crew to escape without loss. Another of her sisters, Kickapoo, rescued the survivors.