Painting of CSS Virginia (left) against the Monitor
The CSS Virginia was a 19th century ironclad employed by the Confederate Navy during the American Civil War. The Virginia later took part in the historic Battle of Hampton Roads, the first battle between ironclad vessels, when it stood off against the United States Navy's USS Monitor.
A painting depicting this battle was stored in the USS Enterprise's library computer in 2254, and was among the materials viewed by the Talosians when they scanned the Enterprise computer. (TOS: "The Cage")
The USS Merrimac, mentioned multiple times in TNG, was named after the ship's original title as a US Navy frigate.