Back where they belong.
While that was my first thought as well, especially as one who grew up in Valley Forge, I have second thoughts.
Given the current trend of affairs and sentiment in this country, perhaps they are safer in private hands.
The flags are indeed owned privately, but through the generosity of the owner will be displayed.
I'm sure some kind soul will set me straight--I believe that the People's Commonwealth of Massachusetts has put a gun lock on a Revolutionary War firearm in the state capitol.