We paid for something when we got there, but it may have been a donation. They have a cool passport set up for kids to mark the state and national parks they've been to. There was also a cute store with all kinds of old toys, recipes, etc.
Yes it is free to tour but do ask if you would like to make a donation
Agreed ^ was donation when i went last April.
It is donation-based, if i remember correctly. They have suggested donations but nothing required.
Thanks! Your answer is awaiting moderation.