Grand Lake St. Mary's State Park

834 Edgewater Drive, St. Marys, Ohio 45885
Park Office Phone: (419) 394-3611
Camp Office Phone: (419) 394-2774
Reservations: (866) 644-6727

Grand Lake St. Mary's State Park Map View

Originally constructed as a feeder reservoir for the Miami-Erie Canal, Grand Lake St. Marys was for many years recognized as the largest man-made reservoir in the world. This large lake is the gateway to swimming, boating, camping and fishing in one of Ohio's oldest state parks.

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You can find more information about each of the following activities below.

Nature Of The Area

Although hard to imagine, at one time the Grand Lake St. Marys region was part of a vast forest wilderness that stretched from the Allegheny Mountains of Pennsylvania to the prairies of Illinois. Today, in place of this forest are fields of corn, soybeans and wheat. In addition to forests, pre-settlement Ohio contained large prairies and wetlands. The land which now lies beneath St. Marys reservoir was once a vast wet prairie. Today, the park contains varying habitats including woodlands, wetlands, and prairies in addition to the surrounding croplands. Perhaps even harder to imagine than vast forests and prairies, is that Grand Lake St. Marys was the site of the first offshore oil drilling in the world. Between 1891 and about 1913, over 100 oil wells had been installed and operated over the waters of the lake. It took the discovery of greater oil reserves in Texas to put an end to Ohio’s oil boom. Download The Geology of the St. Marys Region booklet. Grand Lake St. Marys lies along one of the country's major migration routes. Water birds using the lake as a resting stop include Canada geese, ducks, grebes, swans, egrets, loons, herons, cormorants and ospreys. Many ducks, geese and heron also nest here. Bald eagles, magnificent birds long absent from the area, have again nested on the southwest corner of the lake at the wildlife refuge. Other animals of the park include fox squirrel, mink, raccoon, beaver, coyote, white-tailed deer and many others.


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The campground contains 216 sites of which 135 are equipped with electricity. Facilities include flush toilets, laundry, showers and a dump station. Pets are permitted. The campground also offers a ?camper?s only? swimming beach, boat launch and boat docks/tie-ups. Tow Rent-A-Camps and tow Rent-A-Tepees with camping gear may be rented May-October. Two spacious Cedar Cabins with all the amenities of a fully-equipped RV are also available for daily or weekly rental. A seasonal naturalist holds scheduled programs, including movies, Thursday through Saturday night.

Campground Map

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Swimming, & Boating

Swimming: The park offers four public swimming beaches as well as other swimming areas provided for boaters. Lifeguard coverage is limited to weekends and holidays.

Boating: Boats of unlimited horsepower are permitted on the 13,500-acre lake. A 300-foot no-wake zone has been established and is enforced around the lake's 52 miles of shoreline. Nine state-operated launch ramps provide access to the lake. Several private launch ramps also exist along the shallow shoreline. Seasonal dock rentals are available, call the park office for information.


A valid Ohio hunting license is required. You can find out more information about getting a valid Ohio hunting and trapping license on Ohio's division of wildlife website: Pursuant to Ohio Administrative Code, no person shall at any time hunt, trap, kill, pursue, or shoot at any wildlife and/or wild animals by any means within 400 feet of any nature trail, picnic area, service area, residence, barn, parking lot, cabin, or other structure.

Grand Lake St. Mary's State Park Hunting Map


Picnic areas with tables and grills are located in scenic areas around the lake. Some picnic shelters are on a reservation basis. Contact the park office for details.

History Of The Area

The area in and around Grand lake St. Marys State Park played an important part in the development of the Northwest territory. The St. Marys River served as a vital link between the Great Lakes and the Ohio River. Because of this heavy water traffic, the renegades Simon and James Girty established a trading post, which eventually evolved into the town of St. Marys. General “Mad” Anthony Wayne passed through the area in 1794 during this march to drive out the Shawnee, which culminated in the Battle of Fallen Timbers. Some of Wayne's men returned here to make their homes. In 1837, work commenced on a reservoir for the Miami-Erie canal to maintain the canal’s five-foot water depth. Workers using hand tools were paid 35 cents a day and a jigger of whiskey to keep malaria away. At its completion in 1845, 13,500-acre Grand Lake was the largest man-made lake in the world. The lake was connected to the canal by a three-mile feeder. The canal prospered until the coming of the railroads in the 1870s. The area experienced another boom in the late 1890s when oil was discovered. For a time the lake was dotted with oil derricks. Today a pile of rocks near the center of the lake marks the spot of the last producing well. Grand Lake St. Marys and other canal feeder lakes in the state were the first areas to be dedicated as Ohio state parks in 1949.

Other Area Attractions

Lake Loramie State Park, southeast of Grand Lake St. Marys, offers fishing, boating, swimming and camping. The Miami-Erie Trail, a 47-mile portion of the statewide Buckeye Trail, begins at Lake Loramie and passes within a mile and a half of Grand Lake St. Marys State Park. The Miami-Erie Trail terminates at Delphos, approximately 22 miles north of St. Marys. St. Marys Fish Hatchery, located on the lake's eastern shore is operated by the ODNR Division of Wildlife. The hatchery raises saugeye, walleye, channel catfish and bass for distribution in the public fishing waters of the state. The Neil Armstrong Air and Space Museum is located in Wapakoneta, Armstrong's boyhood home.