Tongue River Reservoir State Park sits along the eastern slopes of Montana’s Bighorn Mountains in Big Horn County, where the Tongue River was dammed to create a striking 12-mile-long reservoir carved into rugged sandstone terrain. At 642 acres, the park wraps around the reservoir’s shoreline, offering a surprising oasis of water recreation in Montana’s semi-arid southeastern plains.

The reservoir is one of the region’s top warm-water fisheries, drawing anglers after walleye, smallmouth bass, crappie, and northern pike. The relatively warm water temperatures also make it one of the few Montana lakes genuinely comfortable for swimming and water skiing during summer months. Boaters will find multiple launch ramps and plenty of open water to explore, while the surrounding bluffs and coulees provide a dramatic backdrop unlike typical mountain-state scenery.

Camping is available at several developed sites along the reservoir’s shores, with options ranging from basic spots near the water to sites with electrical hookups. Reservations are recommended for summer weekends, as the park draws steady crowds from Sheridan, Wyoming, and Billings. Dispersed camping opportunities exist along the reservoir’s less-developed eastern shore for those seeking solitude.

The best time to visit is June through September, when water levels are high and temperatures favor swimming and boating. Spring and fall bring excellent fishing with fewer crowds, though wind can pick up considerably across the open plains.

Expect wide-open skies, warm summer days, and a laid-back atmosphere that feels more like a hidden western lake than a state park.

Explore Nearby

• Red Grade Trails — Public Land in Wyoming
• Bighorn National Forest — National Forest in Wyoming
• Custer National Forest — National Forest in Montana, South Dakota
• Paint Rock Canyon Trail — Public Land in Wyoming