[a] Monitor played a central role in the Battle of Hampton Roads on 9 March under the command of Lieutenant John L. Worden, where she fought the casemate ironclad CSS Virginia (built on the hull of the scuttled steam frigate USS Merrimack) to a stalemate.

The Confederates were forced to scuttle and destroy Virginia as they withdrew in early May 1862 from Norfolk and its naval shipyard, while Monitor sailed up the James River to support the Union Army during the Peninsula Campaign under General-in-Chief George B. McClellan.

The ship participated in the Battle of Drewry's Bluff later that month, and remained in the area giving support to General McClellan's forces on land until she was ordered to join the Union Navy blockaders off North Carolina in December.

[7] Experience during the Crimean War of 1854–1855 showed that armored ships could withstand repeated hits without significant damage when French ironclad floating batteries defeated Russian coastal fortifications during the Battle of Kinburn.

Subsequently, the urgency of Monitor's completion and deployment to Hampton Roads was driven by fears of what the Confederate ironclad, now renamed Virginia, would be capable of doing, not only to Union ships but to cities along the coast and riverfronts.

Northern newspapers published daily accounts of the Confederates' progress in converting the Merrimack to an ironclad; this prompted the Union Navy to complete and deploy Monitor as soon as possible.

The Union Navy advertised for proposals for "iron-clad steam vessels of war" on 7 August and Welles appointed three senior officers as the Ironclad Board the following day.

[15][c] Ericsson originally made no submission to the board, but became involved when Cornelius Bushnell, the sponsor of the proposal that became the armored sloop USS Galena, needed to have his design reviewed by a naval constructor.

[18] Upon review of Ericsson's unusual design, the board was skeptical, concerned that such a vessel would not float, especially in rough seas, and rejected the proposal of a completely iron laden ship.

Wise, Assistant Inspector of Ordnance, advising the use of "liquid fire", scalding water from the boiler through hoses and pipes, sprayed out via the vents and pilothouse window, to repel enemy boarders.

[62] While Ericsson stood on its deck in defiance of all his critics who thought she would never float,[63] Monitor was launched on 30 January 1862 to the cheers of the watching crowd, even those who had bet that the ship would sink straight to the bottom,[64] and commissioned on 25 February.

[70] Because Monitor was an experimental craft, urgently needed, hurriedly constructed, and almost immediately put to sea, a number of problems were discovered during her maiden voyage to Hampton Roads and during the battle there.

[84] On 6 March 1862, the ship departed New York bound for Fort Monroe, Virginia, towed by the ocean-going tug Seth Low and accompanied by the gunboats Currituck and Sachem.

[101] The next morning at about 6:00 am Virginia, accompanied by Jamestown, Patrick Henry and Teaser, got underway from Sewell's Point to finish off Minnesota and the rest of the blockaders, but were delayed from reaching Hampton Roads because of heavy fog until about 8:00 am.

[120] Temporarily blinded by shell fragments and gunpowder residue from the explosion, and believing the pilothouse to be severely damaged, Worden ordered Williams to sheer off into shallow water, where Virginia with her deep draft could not follow.

Jones demanded to know why and was briefed by Lieutenant Eggleston that powder was low and precious, and given Monitor's resistance to shot after two hours of battle, maintained that continued firing at that point would be a waste of ammunition.

The Union Navy chartered a large ship (the sidewheeler USS Vanderbilt) and reinforced her bow with steel specifically to be used as a naval ram, provided Virginia steamed far enough out into Hampton Roads.

[132] On 11 April, Virginia, accompanied by a number of gunboats, steamed into Hampton Roads to Sewell's Point at the southeast edge, almost over to Newport News, in a challenge to lure Monitor into battle.

[134] In a further attempt to entice Monitor closer to the Confederate side so she could be boarded, the James River Squadron moved in and captured three merchant ships, the brigs Marcus and Sabout, and the schooner Catherine T.

[138][139] Monitor was now part of a flotilla under the command of Admiral John Rodgers aboard Galena, and, along with three other gunboats, steamed up the James River and engaged the Confederate batteries at Drewry's Bluff.

At Fox's request, Worden gave a speech to the gathering about his voyage from New York to Hampton Roads, the trials they were faced with along the way and of the great battle between Monitor and Virginia, while paying tribute to many of the officers and men involved.

The orders were received by the crew on Christmas Day, some of whom had been aboard Monitor on her harrowing journey from New York to Hampton Roads in March and were not pleased with the prospect of taking to the high seas once again.

Under the command of John P. Bankhead, Monitor put to sea on 31 December, under tow from the steamship USS Rhode Island, as a heavy storm developed off Cape Hatteras, North Carolina.

Large waves were splashing over and completely covering the deck and pilot house so the crew temporarily rigged the wheel atop the turret which was manned by helmsman Francis Butts.

Realizing the ship was in serious trouble, Bankhead signaled Rhode Island for help and hoisted the red lantern next to Monitor's white running light atop the turret.

Around 160 divers were assigned to remove the parts of the hull, including the armor belt, that lay on top of the turret using chisels, exothermic cutting torches and 20,000 psi (140 MPa; 1,410 kg/cm2) hydroblasters.

[196] Only 16 of the crew were not rescued by Rhode Island before Monitor sank and the forensic anthropologists at JPAC were able to rule out the three missing black crewmen based on the shape of the femurs and skulls.

[202] In 2003 NOAA divers and volunteers returned to the Monitor with the goal of obtaining overall video of the site to create a permanent record of the current conditions on the wreck after the turret recovery.

During the dives, Monitor's iron pilothouse was located near the bow of the vessel and documented for the first time by videographer Rick Allen, of Nautilus Productions, in its inverted position.

The sculptor Antonio de Filippo was commissioned by the State of New York in the 1930s for a bronze statue to commemorate the Battle of Hampton Roads, John Ericsson, and the crew of the ship.