Enjoy a tour of the only state park in the U.S. with a working dairy farm. Tamma Duffy and her husband run Great Brook Farm at Great Brook State Park in Carlisle, MA. Watch as she shows visitors an amazing sight: the only robotic milker on a Massachusetts dairy farm. Her farm is very diversified – she has an ice cream stand, and sells compost, cow manure, loam and cranberries. She explains the importance of local food.