The county contains over of parks, lakes, and publicly accessible forestland. It is drained by two river systems, the Potomac and the Youghiogheny. The Savage River, a tributary of the Potomac, drains about a third of the county. The Casselman River, a tributary of the Youghiogheny, flows north from the county's central section into Pennsylvania. The Youghiogheny itself drains the westernmost area of the county and flows north into Pennsylvania, where it empties into the Monongahela River at McKeesport, just south of Pittsburgh.