[Double turreted ironclad monitor "Onandaga," James River]
After first battles involving of American ironclads (both with wooden ships and with one another) in 1862 during the American Civil War, it became clear that the ironclad had championed the unarmored ship as the most powerful warship. This type of ship would come to be very successful in the American Civil War. This change was pushed forward by the development of heavier naval guns (the ironclads of the 1880s carried some of the heaviest guns ever mounted at sea at the time), more sophisticated steam engines, and advances in metallurgy which made steel shipbuilding possible. An ironclad is a steam-propelled warship protected by iron or steel armor plates used in the early part of the second half of the 19th century. The ironclad was developed as a result of the vulnerability of wooden warships to explosive or incendiary shells. The first ironclad battleship, Gloire, was launched by the French Navy in November 1859. In early 1859 the Royal Navy started building two iron-hulled armored frigates, and by 1861 had made the decision to move to an all-armored battle fleet. The rapid development of warship design in the late 19th century transformed the ironclad from a wooden-hulled vessel that carried sails to supplement its steam engines into the steel-built, turreted battleships and cruisers of the 20th century.
In the early years of the war many civilian ships were confiscated for military use, while both sides built new ships. The most popular ships were tinclads—mobile, small ships that actually contained no tin. These ships were former merchant ships, generally about 150 feet in length, with about two to six feet of draft, and about 200 tons. Shipbuilders would remove the deck and add an armored pilothouse as well as sheets of iron around the forward part of the casemate and the engines. Most of the tinclads had six guns: two or three twelve-pounder or twenty-four-pounder howitzers on each broadside, with two heavier guns, often thirty-two-pounder smoothbores or thirty-pounder rifles, in the bow. These ships proved faster than ironclads and, with such a shallow draft, worked well on the tributaries of the Mississippi.