Milwaukee was 229feet long overall and had a beam of 56feet. The ship had a depth of hold of 8feet[1] and a draft of 6feet. She had 970 tons burthen and displaced 1300LT.[2] Her crew numbered 138 officers and enlisted men.[3]
The ship was powered by two 2-cylinder horizontal non-condensing steam engines, each driving two propellers, using steam generated by seven tubular boilers. The engines were designed to reach a top speed of 9kn. Milwaukee carried 156LT of coal.[2]
The ship's main armament consisted of four smoothbore, muzzle-loading 11-inch Dahlgren guns mounted in two twin-gun turrets.[3] Her forward turret was designed by James Eads and her rear turret by John Ericsson.[1] Each gun weighed approximately and could fire a 136lb shell up to a range of at an elevation of +15°.[4]
The cylindrical turrets were protected by eight layers of wrought iron 1inches plates. The sides of the hull consisted of three layers of one-inch plates, backed by of pine. The deck was heavily cambered to allow headroom for the crew on such a shallow draft and it consisted of iron plates thick. The pilothouse, positioned behind and above the fore turret, was protected by of armor.[5]
James Eads was awarded the contracts for all four of the Milwaukee-class ships. He laid down Milwaukee at his Union Iron Works Carondelet, St. Louis in 1862.[3] The first U.S. Navy ship to be named after the Wisconsin city, she was launched on 4 February 1864 and commissioned on 27 August 1864. Acting Volunteer Lieutenant James W. Magune was in command.[6] Milwaukee was initially assigned to the Mississippi Squadron upon commissioning, but saw no action before she was ordered south to join West Gulf Blockading Squadron. The ship departed Mound City, Illinois on 15 October and arrived at New Orleans, Louisiana 12 days later. Lieutenant Commander James H. Gillis relieved Magune on 22 November.[6] She was still under repair there on 27 November, although Milwaukee reached Mobile Bay by 1 January 1865.[7]
Although the victory at the Battle of Mobile Bay on 5 August 1864 had closed the port of Mobile to blockade runners, the city itself had not been taken. The Confederates fortified the approaches to the city and heavily mined the shallow waters surrounding it. On 27 March 1865, Milwaukee, together with several other Union ships, sortied upriver in an attempt to cut communications between Spanish Fort and Mobile.[6] The following day she and her sister ship 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,, rescued the survivors.[8]
In 1868 the wreck was raised and towed to St. Louis and broken up; her iron was used in the construction of the Eads Bridge across the Mississippi River.[6]