ISO a good boardgame for my father-in-law

Hello my dear readers,

I apologize in advance for this open and somewhat off-topic request, but I trust your indulgence and broad knowledge of everything-wargaming as I work on my Christmas list…

My wife suggested that, as a present for my father-in-law, we look into a military boardgame. I have been concentrating on miniatures for two decades now, and my Avalon Hill days are long gone, so I am not really sure what to look at. My father in law is a retired high school principal, with a keen interested in American history, in particular AWI and ACW. He never played wargames before, but he seemed genuinely interested to my gaming hobby. I do not expect him to pick up brushes and miniatures, hence the idea to proceed with a boardgame first. Ideally, I'd love to find a game with the following features:

a. good/high solitaire playability;
b. very good historical background;
c. medium complexity: something engaging for an adult, not too simplistic yet not too overwhelmingly complex;
d. focus on the American War of Independence or the American Civil War.

I am sure that, out there, there must be a "present day" AH "1776"… I just don't know where to look. Any suggestion & recommendation will be greatly appreciated – and hey, if any winning idea will come, I'll buy you a drink at Historicon!

Thanks in advance!