Fort Necessity is really quite interesting. It is the site of a battle at the start of the French and Indian War in 1754. When I visited there was an encampment, where people dressed up in period costume, fired muskets and explained a bit of the history of the fort.
I found out that at this very site, Colonial troops, at that time on the side of the Brits (Hoorah!), led by George Washington, fought the opening battle of this war. The Frnech and Indian War was a struggle between Great Britain and France for control of North America. This particular battle was sort of an impromptu thing, and resulted in the hasty building of a stockade. It was this last minute thing that gave the place its name of Fort Necessity. The history lesson that we received went on to explain that Washington surrendered to the French at this battle.
I don't know whether the excellent explanation happens every day, or whether it was because there was an encampment at the time, but it really brought some "depth" and "colour" to the location.