Sid Meier's Gettysburg was a remarkable wargame that managed to balance realism and accuracy with a user-friendly design and stylish visuals. Sid Meier's Antietam is also an impressive game that builds upon the foundation established by the original.
Civil War Generals 2 is a turn-based Civil War game from the now-defunct Sierra Entertainment that doesn't try to break down the conflict into just one or a few battles: it gives you everything. 46 scenarios spread across the east and west spheres of conflict.
War is not fair -thus is one of the many interesting quotes that Warfare 1917 throws at its' players, and it is true. The computer AI will relentlessly push forward with a myriad of troops, and artillery bombardment is a constant danger to all you men.
Take Command: Second Manassas is a title that doesn't even dare to adhere to the expected wargame format. In fact, it is a rather unique real-time strategy that lets you command a variety of units on a battlefield in north Virginia.