Yesterday was the 159th anniversary of the Battle of Hampton Roads, the first battle between ironclad warships and quite possible one of the most influential engagements in naval history. The Monitor's last minute arrival at Hampton Roads and rescue of the Union fleet is one of the most amazing and heroic stories of the civil war, and it's personally responsible for sparking my interest in military history and technology.
Article on the historical context here: The Day Iron Ships Went to War | National Review
The battle was also depicted in the mostly-accurate 1991 film Ironclads, one of the few films to focus on the naval aspect of the civil war as opposed to the ground war.