American Civil War
I have only visited two U.S. Civil War battlegrounds, but to do so I had to trick my girlfriend at the time (while we were on holiday in America 1999) that it was a shorter trip to drive from Washington up to New York through Pennsylvania.
On the way to New York I discovered two different battlefields, Antietam and Gettysburg. We first visited Antietam, but there was only a small museum and a short tour that you could take in your own car. After that we went to Gettysburg, which was a larger town with a big museum and a lot of motels.
We stayed at a motel across the street from the big museum; the room was cheap and clean but very cold. In the early morning we took a map and went on a big tour around the battlefield. There were A LOT of monuments, I can tell you - but I guess the Americans have a thing for monuments. We stopped at the museum, which was very good, and finished at Little Round Top where you had a great view over the countryside.