25 October 1861: Keel of the USS Monitor is laid.

On this day in 1861, signaling an important shift in the history of naval warfare, the keel of the Union ironclad Monitor is laid at Greenpoint, New York.

Union Secretary of the Navy Gideon Welles appointed an Ironclad Board when he heard rumors that the Confederates were trying to build an iron-hulled ship, as such a vessel could wreak havoc on the Union’s wooden armada. In September 1861, the board granted approval for engineer John Ericsson, a native of Sweden, to begin constructing the U.S. Navy’s first ironclad.

The wooden keel was laid at the Continental Iron Works at Greenpoint. Carpenters worked around the clock on the frame while the iron sheathing was prepared for the hull. The vessel was not large—172 feet long and 41 feet wide—but its design was unique. The craft had an unusually low profile, rising from the water only 18 inches. A 20-foot cylindrical turret in the middle of the ship housed two 11-inch Dahlgren guns that topped the flat, iron deck. The ship had a draft of less than 11 feet so it could operate in the shallow harbors and rivers of the South.

Ericsson pushed the production to be as speedy as possible, but he could not deliver the ship by the January 12, 1862, delivery date. It was finally launched into New York’s East River on January 30. Many small engine problems also needed to be solved before the craft was commissioned on February 25. The Monitor sailed for Virginia soon after, arriving at Chesapeake Bay on March 6. On March 8, 1862, it engaged in one of the most famous naval duels in history when it clashed with the Confederate ironclad the Virginia(which had been constructed from the captured Union ship Merrimack). A day of heavy pounding produced a draw; each ship was immune from the other’s shots. A new naval era had dawned.