Frank Hunter gave me permission in August 2004 to offer his ACW game as a free download.
To download American Civil War version 2.66, dated 30 September 2003, right-click here. It's a 5.25 MB zip file.
To install, just unzip the files into an empty folder. To run, double-click the Acwiii.exe file. The download includes the official manual for the game as a PDF file, which is worth reading but doesn't give all the information that you might want.
Rusty Coleman has provided me with an alternative version of the Acwiii.exe file. He says Frank sent it to him in 2004 and it contains a bug fix related to "some sort of production glitch". I haven't tried it myself but you can download it by right-clicking here. It's a 3 MB zip file. It still identifies itself as version 2.66, but it is a different file. This is just the executable file; you still need the other files provided in the other zip file.
Frank plans a completely rewritten version of his ACW game someday, but it's not imminent: he has other games to work on first.