As the largest lake in Armstrong County, Keystone Lake covers 850 acres and stretches 5.5 miles. While the deepest part of the lake is 90 feet deep, the lake also features shallows and wetlands. Owned and operated by Reliant Energy as a cooling water supply for Keystone Power Plant, the lake and surrounding area are open for public use. The area is controlled by the PA Fish & Boat Commission, which means all of their rules and regulations are in effect. Swimming is prohibited, but boats up to 20 HP are permitted.
The lake has two formal boat launches with large parking areas: NuMine (north shore) off of Route 85 at White Oak Road and Atwood (south shore) off of Route 210 in the borough of Atwood. There are also several primitive access areas around the lake.
Keystone Lake provides an excellent warm water fishery with large and smallmouth bass, walleye, musky, perch, crappies, bluegills, sunfish, pumpkin heads, and trout (stocked). As a trophy bass lake, several professional tournaments have been held here.
Several thousand acres surrounding the lake are open to hunting, where PA Game Commission laws and regulations apply. When winter weather conditions permit it, the lake is also a wonderful place for ice fishing.