The only good American Civil War themed game that I could remember was Gettybursg.
War of Rights could be that next good American Civil War game. It will focus mostly on Maryland Campaign of September 1862. The game uses CryEngine.
The developer, Campfire Games, has an ambitious plan. According to the studio, “With War of Rights, we are focusing on creating a group-based game with real Napoleonic-era tactics combined with the deadly accuracy of the “newer” weapons available in the period of the Civil War. Uniforms, equipment, artillery, houses, fields, and the locales are all portrayed as faithful as possible to the period we’re showcasing in the game. All of this is thanks to the marvel that is the system of the CRYENGINE. Players will form companies and regiments and battle each other on the iconic locations of battlefields such as Antietam, South Mountain, and Harper’s Ferry, following the chain of command from the rank and file private all the way up to the Major General.”
Gamers interested in the Kickstarter can visit the official page.