Though the most famous battles of the Civil War occurred on land, from the beginning both sides recognized that control of the seas would be crucial. This was due to the agriculturally based Southern economy that relied on shipping to receive goods and supplies. Once the Civil War began, President Lincoln ordered a blockade of Southern ports. The South responded to the North's strategy by "blockade running," which became the only way the Confederate states could supply themselves with direly needed wares. Ships filled with goods--some for the war effort, others for Southern consumers--left Nassau, the Bahamas; Havana, Cuba; the West Indies; and Bermuda attempting to sneak by the Union Navy. However, the Union Navy succeeded in closing many harbors such as Mobile, Alabama, which was deep enough to accommodate large ships.

The U.S. Navy had to grow rapidly to perform its roles. Though in 1861 it consisted of just 42 warships, by 1865 it had grown to 675 vessels. The North converted ships originally designed for other functions, such as whalers and tugs, and built others from scratch, many of which adopted the latest technology. The most famous example of innovation was the ironclad or "monitor" ships, which were named after the first vessel of its kind. The USS Monitor and subsequent, similar warships were armored with iron plate that was supposed to make them hard to sink. Union warships gradually added other features, including steam engines and more powerful guns. To counteract the Union Navy, the Confederates introduced a new weapon, which they called a "torpedo." Torpedoes were cheap, easily produced underwater mines that could seriously damage or sink ironclad ships.

The Union's armored ships and the Confederate's torpedoes clashed in combat during the summer of 1864 at Mobile Bay in Alabama. In July, Admiral Farragut prepared to lead the Union Navy in an attack on Fort Morgan, which guarded the mouth of Mobile Bay. In the previous two years he had seized New Orleans and Galveston, and he was now ready to close the last major port still available to blockade runners on the Gulf of Mexico.