The USS Monitor, a Civil War-era warship, was designed and built in just 4 months. - Apparently.
The USS Monitor was a revolutionary ironclad warship designed by Swedish-American engineer John Ericsson, who had a vision for a ship with a rotating turret to allow for 360-degree fire. Commissioned in February 1862, the Monitor played a crucial role in the Battle of Hampton Roads, but sank in a storm off the coast of North Carolina in December 1862. The speed and efficiency of its construction remain an impressive feat in naval history.