St. Mary’s River State Park

Southern Maryland’s 250-Acre Lake — 7.5-Mile Trail Loop, Bass & Pickerel Fishing, Mountain Biking & Horseback Riding Near Leonardtown

St. Mary’s River State Park is a day-use park centered on a 250-acre freshwater lake in St. Mary’s County, Maryland, near Leonardtown. The park is divided into two areas: the developed Lake Area (Site 1) with a boat launch, picnic facilities, and a 7.5-mile multi-use trail loop circling the lake; and the undeveloped Hunting Area (Site 2), a forested tract managed for wildlife habitat and seasonal hunting.

The 7.5-mile lake loop trail is the park’s signature feature — a well-maintained path suitable for hiking, mountain biking, and horseback riding that circumnavigates St. Mary’s Lake through mature hardwood forest. The lake itself supports an excellent largemouth bass, chain pickerel, crappie, and sunfish fishery restricted to electric motors only, ensuring a quiet, natural experience on the water. For residents of Southern Maryland and the D.C. region, St. Mary’s River State Park provides a genuine woodland escape in a county better known for its Chesapeake Bay shoreline.

Things to Do

Fishing

St. Mary’s Lake (250 acres) is a productive warm-water fishery:

• Species: Largemouth bass (slot length limit applies), chain pickerel, crappie, bluegill, and sunfish
• Electric motors only: No gasoline-powered boats — ensures a quiet fishing environment
• Boat launch ramps available at the Lake Area
• Note: Fishing is prohibited on the spillway below the dam
• Maryland fishing license required

Hiking & Trail Riding

The park’s signature 7.5-mile loop trail encircles St. Mary’s Lake:

• Multi-use: Open to hiking, mountain biking, and horseback riding
• Terrain: Rolling hardwood forest with lake views; moderate difficulty
• Well-maintained and well-marked

Boating & Paddling

• Electric motors only: Kayaks, canoes, and electric-motor boats welcome
• Boat launch ramps at the Lake Area
• The 250-acre lake offers excellent flat-water paddling through forested shoreline

Wildlife & Nature

• Birding: The lake and surrounding forest attract warblers, herons, osprey, and woodpeckers
• Hunting Area (Site 2): Seasonal hunting permitted in the designated area — check Maryland DNR for seasons and regulations
• Leashed pets welcome

Best Time to Visit

Visitor Tips

• Day-use only: St. Mary’s River State Park has no camping. It’s a day-use park with a boat launch, picnic areas, and trails. Plan for a half-day or full-day visit.
• Electric motors only: The 250-acre lake restricts all watercraft to electric motors — no gas-powered boats. This creates an exceptionally quiet fishing and paddling environment. Bring an electric trolling motor or paddle in.
• 7.5-mile loop: The lake loop trail is the main attraction for hikers, mountain bikers, and horseback riders. Allow 2–3 hours for hiking, less for biking. Well-maintained and well-marked.
• Bass slot limit: Largemouth bass have a protected slot length limit — check Maryland DNR regulations before fishing. This regulation helps maintain the quality of the fishery.
• Automated entry: Admission is collected via an automated gate system that accepts credit/debit cards only — no cash. Be prepared.
• Hunting Area caution: The Hunting Area (Site 2) is active during Maryland hunting seasons. If hiking in that area during fall/winter, wear blaze orange and check hunting season dates with Maryland DNR.

Frequently Asked Questions

Last updated: April 2026