The Ironclad Board was an advisory board, established by the Union, in which year, in response to the construction of the "CSS Virginia" by the Confederacy during the US Civil War,primary goal of the Ironclad Board was to develop more battle-worthy ("ironclad") ships, including the USS Monitor, an iron-hulled steamship?
USS Monitor USS "Monitor" was an iron-hulled steamship. Built during the American Civil War, she was the first ironclad warship commissioned by the Union Navy. "Monitor" is most famous for her central role in the Battle of Hampton Roads on 9 March 1862, where, under the command of Lieutenant John Worden, she fought the casemate ironclad  (built on the hull of the former steam frigate USS "Merrimack" ) to a standstill. The unique design of the ship, distinguished by its revolving turret which was designed by American inventor Theodore Timby, was quickly duplicated and established the monitor type of warship.
USS Mahopac (1864) USS "Mahopac" was a single-turreted "Canonicus"-class monitor built for the Union Navy during the American Civil War. The vessel was assigned to the James River Flotilla of the North Atlantic Blockading Squadron upon completion in September 1864. The ship spent most of her time stationed up the James River where she could support operations against Richmond and defend against sorties by the Confederate ironclads of the James River Squadron. She engaged Confederate artillery batteries during the year and later participated in both attacks on Fort Fisher, defending the approaches to Wilmington, North Carolina, in December 1864 – January 1865. "Mahopac" returned to the James River after the capture of Fort Fisher and remained there until Richmond, Virginia was occupied in early April.