Grand Lake St Marys State Park is one of the Ohio 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
Grand Lake St Marys State Park is in Mercer County, Ohio. Its approximate coordinates are 40.52002, -84.49974.
Check in at Grand Lake St Marys State Park
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.