McConnells Mill State Park, in Lawrence County, encompasses 2,546 acres of the spectacular Slippery Rock Creek Gorge. Created by the draining of glacial lakes thousands of years ago, the gorge has steeps sides and the valley floor is littered with huge boulders and is a national natural landmark. Slippery Rock Creek is a Class II to IV river, depending on water level. Spring and fall are the best times for whitewater boating. A gristmill built in the 1800s is open for tours. McConnells Mill State Park is open from sunrise to sunset, year-round.