CR #21 is one of the Massachusetts parks in thicket's catalog. thicket is a field guide to the parks near you: it maps the ones you have never noticed, gives you a reason to actually go, and keeps a record of where you have been.
Where it is
CR #21 is in Essex County, Massachusetts. Its approximate coordinates are 42.69746, -70.99029.
Check in at CR #21
thicket verifies you are actually here by GPS when you check in, so a visit means you went. Checking in builds a streak, earns achievements, and fills in your map of the places you have been.