Kirby makes an excellent point, if left to the resources of only individuals; we would have little to nothing left of these battle fields. The Civil war Preservation Trust (http://www.civilwar.org/) has been a great organization that has preserved a lot of land that blood was shed on by both sides.
The NPS has its faults, and a lot of bantering back & forth about HOW these sacred grounds are "interpreted", but the funding they can funnel into the battleground parks makes sure some of the land is not encroached on. Drive around Kennesaw NP in Georgia...Houses/Developments go right up to the national boundary!
I know “Stimulus” money from the present administration has been allocated to the National Park system, at least (without a major debate here on THAT subject) that should hopefully defray major cut-backs to services at WBTS parks.
I have seen State Parks like Pickett's Mill State Park in Georgia modify it's open/close hours due to cut backs in State funding.