Mary Island is one of the New York 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
Mary Island is in New York. Its approximate coordinates are 44.36554, -75.92180.
Check in at Mary Island
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.