The Passaic Class of monitor ships featured thicker hull plating, larger guns, better steering, and an improved pilot house design. The new monitors were larger than the original, measuring 200 feet by 45 feet in the beam. The hull, designed with more shiplike lines, in contrast to the original monitor's nearly flat bottom. The most noticeable change was to the pilot house, which was enlarged to six feet in diameter and mounted atop the turret.

USS Monitor was the first ever ironclad warship commissioned by the United States Navy. She is most famous for her participation in the first-ever naval battle between two ironclad warships, the Battle of Hampton Roads on March 9, 1862 during the American Civil War, in which Monitor fought the ironclad CSS Virginia of the Confederate States Navy.

A non-Ericsson twin-turret design. Constructed by Continental at Greenpoint NY. Launched 29 Jul 63. Commissioned 24 Mar 64. James River flotilla. Fitted with a locomotive headlight on the bow. Convoyed Butler's troops up James R. 5 May 64. Engagement at Trent's Reach 21 Jun 64. Engagements at Dutch Gap 13, 16-18 Aug 64. Bombarded Howlett's Battery 29 Nov 64 and 5-6 Dec 64. Engaged CSS Virginia II, Richmond, and Fredericksburg on 24 Jan 65, forcing them to retire. Decommissioned 8 Jun 65. Sold to vessel's designer, George Quintard, who sold it to France 12 Jul 67; refitted with breechloading guns. Broken up 1903.

Under the direction of the Chief of Naval Construction, John Lenthall and the Chief of Steam Engineering, Benjamin F. Isherwood, the Roanoke began an extensive modification at Novelty Iron Works, N.Y. Roanoke was cut down to a low-freeboard ship and given three revolving Ericsson centerline turrets. Instead of the usual series of 1 in. laminated plates for hull armor, Roanoke featured one-piece 4.5 in. slabs.

USS Galena, an ironclad screw steamer, was one of the first three ironclads, each of a different design, built by the Union Navy during the American Civil War. She had an unconventional armor plating arrangement which proved ineffective. Her keel was laid down by H.L. and C. S. Bushnell of Mystic, Connecticut. She was launched on 14 February 1862, and commissioned on 21 April 1862 with Commander Alfred Taylor in command.

USS Keokuk, an experimental ironclad steamer, was the only ship of the United States Navy to be named for the city of Keokuk, Iowa. Her keel was laid down at New York City by Charles W. Whitney, with the name Moodna (sometimes incorrectly spelled "Woodna"). she was renamed while under construction, launched in December 1862 sponsored by Mrs. C. W. Whitney, wife of the builder, and commissioned in early March 1863 with Commander Alexander C. Rhind in command.

USS New Ironsides was a broadside ironclad United States Civil War ship, named in honor of USS Constitution, which earned the nickname "Old Ironsides" during her engagement with HMS Guerrière in the War of 1812. It was built in 1861 by Merrick & Sons at the C.H. and W.H. Cramp shipyard in Philadelphia, Pennsylvania, the last and largest of an initial group of three ocean-going ironclads ordered to meet the needs of the Civil War.