Boston boasts some of the best museums, zoos, and theme parks in America, but those cool experiences can come at a steep cost. But here's a secret: Many museums and attractions in Massachusetts are free for little kids, and in some cases, all kids. Mommy Poppins has set out to uncover these freebies—54 of them, in fact!

If you're working your way through our Boston Kids' 100 Things to Do bucket list, you may want to coordinate with the cut-off ages below; some of the museums you can catch on their free admission days, but several other attractions really drive home the bittersweet point that you're only young once. Don't miss our Boston Free Fun Guide for even more ideas for creating special experiences for kids without breaking the bank.