This is an important story: "Legislation signed into law last year [in Wisconsin] requir[es] money donated to any one of the eight state-operated historic sites be used at that site."
You wouldn't think a law like that would be needed but consider the situation in your own state. Here in Maryland, donations to any state-run ACW site are managed by a recreation department. Does the money go to hiking trails, the general state budget, or to the park donated to? More from Wisconsin:
There was a concerted push for that legislation, and a state commission recommended it, after former Gov. Scott McCallum ordered the Wisconsin Historical Society to send 10% of all its earned revenue to the state general fund to help balance the state budget. That hit the historic sites hard, and they were already hurting from nearly a decade of declining attendance and revenue.
"It's difficult to recruit private donors and sponsors when they think the state will take the money away. Now funds going to the sites are protected."
When the lottery was introduced in New Jersey, critics scoffed at promises of funds earmarked for education. The state constitution forbade earmarking; all funds collected by the government had to go into the general fund. There are complex workarounds to this, and they involve estimating, then apportioning, and then a little sleight of hand.
If you are visiting a state battlefield it may pay to ask before you donate.