EASTERN SEABOARD (WHTM) — For centuries the seas were ruled by “wooden ships and iron men.” Naval battles took place between wooden-hulled sailing vessels bristling with rows of cannons, firing “broadsides” at each other. This continued well into the 19th Century. (The U.S. Navy’s last all-sail vessel, the sloop of war U.S.S. Constellation may be seen at Inner Harbor in Baltimore. She was launched in 1854.)

160 years ago today, everything changed abruptly.

The change was already coming gradually. Steam propulsion first supplemented, then supplanted sails, first with paddlewheels, then with screw propellers. Shipbuilders experimented with replacing wooden hulls with iron. The U.S. Navy’s first iron-hulled warship was the U.S.S. Michigan, a paddle wheeler launched in 1843. (Renamed Wolverine in 1905, she served for 11 years as a training vessel for the Pennsylvania Naval Militia.)

In 1959 the French Navy launched Goire-the first “ironclad” warship. With ironclads, the metal wasn’t there to replace a wooden hull; it was there as armor. (Many early ironclads had iron covering a traditional wooden hull.) Soon fleets around the world we’re building them. But these ironclads still had full sets of sails, and still relied on the broadsides for fighting.

Until March 9, 1862, though, no ironclad fought another.

The United States of America and the Confederate States of America were slugging it out in the second year of the American Civil War. The Union, fully aware of how much the Confederacy relied on manufactured goods from overseas, had initiated the “Anaconda Strategy”, blockading Southern ports and gaining control of the Mississippi River to cut off the Confederacy from outside supplies, without which it could not survive.

The Confederacy somehow had to break the blockade. Stephen Mallory, the Confederate Secretary of the Navy, decided the best use of his limited resources was to build ironclads to contest the still largely wooden-hulled Union blockade. And as it happened, he had some wreckage he could exploit.

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When Virginia seceded from the Union in 1861, the U.S. Navy tried to destroy everything at the Gosport Navy Yard in Portsmouth, Virginia which might be of use to the Confederates. (One of the ships burned as a result was the first U.S.S. Pennsylvania, a ship of the line.) But some important things survived-the shipyard’s drydock, and the most useful parts of the frigate U.S.S. Merrimack. Merrimack was burned to the waterline and sunk, but the Confederates salvaged the wreckage and found the hull below the waterline and the engines were still intact. The wreck was moved into the drydock, the burned parts were stripped away, and the conversion of U.S.S. Merrimack into C.S.S. Virginia began.

What came out of the drydock was, for the time, one of the strangest warships ever seen. Gone were mast and sails; Virginia relied totally on steam power. Both bow and stern were submerged when underway. At the bow was an iron ram. All the firepower was enclosed in a casemate made of 24 inches of oak and pine in layers, covered with two 2-inch layers of iron plating arrayed crisscross to each other. The sides of the casemate were built at a 36-degree angle to deflect enemy fire. Virginia had 14 gunports, three each at bow and stern (to accommodate swivel guns) and four on each side. In other words, it was designed primarily to fire good old-fashioned broadsides.

The Union, meanwhile, was building their own ironclad-a task becoming more urgent as word of Virginia leaked out. If the design of Virginia was unusual, U.S.S. Monitor was revolutionary. Designed by Swedish-American inventor Jon Ericsson, the Monitor had no sails (despite the insistence of Navy old-timers) a shallow draft, a flat bottom, and a flat deck that barely stuck out the water. On the deck, just two guns-but these were mounted inside Monitor’s major innovation-a revolving turret. (The turret was invented by an American, Theodore Timby, who received a 5 percent commission of $13,500.)

On March 8, 1862, C.S.S. Virginia, commanded by Commodore Franklin Buchanan, left her dock and sailed into Hampton Roads, a natural harbor where the Elizabeth, Nansemond, and James rivers empty into the Chesapeake Bay. Ships of the U.S. Navy were stationed there on blockade duty.

By nightfall, the wooden navy was obsolete.

Virginia first attacked the U.S.S. Cumberland, a sail-powered wooden frigate. A prolonged exchange of cannon fire left Cumberland a crippled wreck, her shots doing only minor damage to her opponent. Virginia then finished off the frigate by ramming her. (Virginia’s arm was broken off, which would cause problems later.) The Confederate ship then turned its attention on U.S.S. Congress, which ran aground while attempting to move to shallower water. Congress surrendered after trading fire with Virginia for an hour, but in a breach of war protocol, a Union shore battery opened fire in Virgina while crewmen of Congress were being ferried ashore. In retaliation Buchanan, who’d been injured by the shelling, ordered heated shot fired, which set the Congress on fire. Virginia then tried to attack U.S.S. Minnesota, which had also run aground trying to flee the ironclad. But because of its 22-foot draft, Virginia couldn’t close on its target and returned to port, prepared to return the next day and destroy the rest of the blockade. Lieutenant Catesby ap Roger Jones took Buchanan’s place as commander.

But when Virginia returned the next day, the Monitor, under the command of Lt. John Lorimer Worden,’ was waiting. She had arrived during the night, rushed down from Brooklyn Navy Yard. As Virginia approached the blockaders, Monitor appeared from behind Minnesota and placed herself between Virginia and the grounded ship.

For four hours the two ships circled around each other, pounding away at each other at point-blank range, rarely more than 100 yards apart. (In fact, they actually collided five times.) Both ships has problems; Virginia’s length, draft, and weight made her difficult to turn-her turning radius were about a mile, and it took her around 45 minutes to do a full circle. (The fact the Merrimac’s engines functioned so badly they’d been slated for a replacement didn’t help.) At one point in the conflict, she actually ran aground.

The Monitor’s turret, for its part, was having some teething problems. Something went wrong with the linkage connecting the turret to the steam engine, making it hard to start and stop rotation. The gun crew just let the turret turn and fired their guns as they came in sight of Virginia

The most serious damage-and worst injury came when Virginia scored a hit on Monitor’s pilothouse, temporarily blinding Worden. Crew members on both ships suffered from the noise of shells hitting armor.

At the end of the battle, both ships went back to their mooring places. Both sides declared victory; most experts consider the battle a tactical draw.

The two ships never fought again. The Virginia was trapped in the James River when Union forces gained the upper hand around Hampton Roads. On May 11, 1862, she was scuttled by setting off an explosion in her powder magazine. Though her precise position is known, few artifacts exist, the ship having been heavily salvaged-or perhaps scavenged after the war.

The Monitor was also lost. On December 31st, 1862, she sank off Cape Hatteras, North Carolina, with the loss of 16 crew members. on August 27, 1973, 111 years after she sank, her wreckage was discovered by an expedition mounted by the National Geographic Society and National Science Foundation. Large portions of the ship, including the turret, have since been raised. Most of these now reside at the USS Monitor Center of the Mariner’s Museum and Park in Newport News, Virginia.

Even though the battle was a draw, it revolutionized naval warfare. Ironclads, and later steel-hulled ships, replaced wooden vessels, and rotating turrets replaced broadsides. “Monitor” became a class of vessel, some of which saw service well into the 20th century. And every modern surface warship, of every size, of every class, of every nation, can trace their designs back to the Monitor and Virginia.