Retention of such seemingly obsolete vessels was not as absurd as it may seem. Steam propulsion, a technology still evolving past infancy, suffered from a few tactical issues. Among those was slow speed handling in exactly the tight formations in which doctrine called for the battle divisions to fight. Yes, just as Army officers looked back to the Napoleonic wars for components of their tactics and doctrine, many naval officers considered Nelson's battle line in regard to dispositions. And certainly around appropriations time, many noted place of honor the ship-of-the-line retained even as steam power prevailed.
(Contemporary Illustration of the USS Pennsylvania - Wikipedia commons)
The USS Pennsylvania, laid down in 1822 and commissioned in 1837, was the largest sailing warship ever built in the United States. Rated as a 120-gun ship, by 1860 she was laid up in Norfolk as a receiving ship. If fitted out for war, the Pennsylvania would mount an impressive mix of 8-inch shell guns and 32-pdr cannon. But she was not ready for war as the secession crisis loomed.
Also laid up at Norfolk were the 74-gun ships USS Columbus and USS Delaware. The Columbus was completed in 1819 and commissioned in 1828, the Delaware actually carried 84 guns. A sister ship of the Delaware, the New York was, according to some sources, laid up incomplete at Norfolk. But the Naval records indicate the partially completed vessels was in the New York shipyard. Regardless the New York was never actually commissioned into the U.S. Navy.
(USS North Carolina - Wikipedia commons)
The USS North Carolina served as a storeship in at the New York Navy Yard. Another 74-gun ship, the USS Ohio which dated to 1820, lay in Boston as a receiving ship. Other ships of the rate - the Alabama, Vermont, and Virginia - lay incomplete and thus not commissioned on the stocks. And at Sacketts Harbor, New York, the New Orleans, a 120-gun rate, remained incomplete as the sole Great Lakes ship-of-the-line.
Of the American ships-of-the-line, the Columbus,, North Carolina, and Delaware saw substantial service before the Civil War. The Columbus and Ohio were active during the Mexican War. Like the American frigates, the American 74s often carried guns in excess of their rate. The North Carolina reportedly carried over 100 guns during some Mediterranean cruises.
As indicated, at the time of South Carolina's secession in December 1860, none of these vessels were ready for service. Faced with other operational concerns, the Navy let the ships remain either on the stocks or in yard support capacities right up to the start of the Civil War. The Navy burned the Pennsylvania and Delaware when Virginia state troops took over Norfolk in April 1861, somewhat symbolically marking the end of the ship-of-the-line era.
(USS New Hampshire as receiving ship - Wikipedia commons)
However, a few of the big old sailing ships continued to serve as store ships or receiving ships until the end of the Civil War. The Alabama became the USS New Hampshire, and was commissioned as a store ship. The New Hampshire and Vermont served on station at Port Royal, South Carolina, reportedly receiving heavy caliber Parrott rifles.
As the U.S. Navy entered 1861, in spite of their reserve status these ships-of-the-line were proud measures used to compare with foreign navies. However, during the Civil War the Navy found more use for the ship's holds than the big ship's cannons.