Factual error: The train that pulls into Newton Station with Confederate soldiers has freight cars of modern construction. This can be seen by the newer type trucks, unlike the 'arch-bar' trucks of the period.
Factual error: Atop the desk in the Captain's stateroom is a model of a 5"/25 wet mount gun. The 5"/25 was designed for, and mounted on, U.S submarines; however, it was not introduced into service until 1944, and this is set at the start of World War 2.
Factual error: It appeared that, during the engagement with the Serapis, every hit by either ship's guns resulted in an explosion and fire. Unfortunately, explosive shells wouldn't be used on shipboard (aside from bomb vessels) until the next century.