Originally constructed as a feeder reservoir dug by hand for the Miami & Erie Canal, Grand Lake St. Marys was the world's largest reservoir when built. The region played an important role in opening up the Northwest Territory as the St. Marys River was a vital link between the Great Lakes and the Ohio River.
The park offers 52 miles of shoreline for boating and fishing, as well as a family campground, swimming pool, and picnic areas.
The 13,500-acre lake allows unlimited horsepower. A 300-foot no-wake zone has been established and is enforced around the lake’s 52 miles of shoreline.
Eight state-operated launch ramps provide access to the lake. Several private launch ramps also exist along the shallow shoreline. Seasonal dock rentals are available from April 1 to Oct 1. Call the park office for additional information.
The state wildlife refuge, located on the southwest corner of the lake, is off limits to boats at all times.
Grand Lake St. Marys Campground offers Cedar Cabins and Camper Cabins as well as Full Hook-up, Electric, and Non-electric sites for all types of camping. Pets are permitted in most areas and a dog park is located in the campground. Other amenities include pool, splash pad, and a boat launch. Reservations are required and may be made up to six months in advance, online or by calling (866) 644-6727.
Two fenced dog parks are available. On the East Bank is the Fur-Ever Friends Dog Park. On the West Bank is the Celina Rotary Dog Park. Both offer a place for your dog to frolic without a leash. The campground also offers a dog park for registered campers only.
Largemouth bass, white and black crappies, bluegills, walleye, channel and flathead catfish, yellow perch, bullheads, and carp are found in the lake. Gizzard shad is the primary forage species for predators.
- An accessible fishing pier is available at East Bank
- An accessible fishing access area is located at West Bank
- Ohio fishing regulations apply.
- A valid Ohio fishing license is required (16 and older).
Limited hunting is permitted in designated areas.
- 70 seasonal duck blinds are available in a controlled hunt managed by ODNR Division of Wildlife.
- Ohio Hunting and Trapping Regulations
- A valid Ohio hunting license is required.
Several picnic areas with tables and grills are located in scenic areas around the lake on a first-come, first-served basis. Some are covered.
Four shelterhouses that can be reserved online or by calling (866) 644-6727.
Four public swimming beaches are available. Swimming is permitted during daylight hours only. Visitors swim at their own risk. Pets are not permitted on swimming beaches. Other swimming areas are also provided for boaters.
- BeachGuard — Water quality advisories, Memorial Day to Labor Day, from Ohio Dept. of Health
The park offers three trails:
- West Bank Multi-use Trail - 1.2 miles. Easy, paved, accessible
- East Bank Multi-use Trail - 1.4 miles. Paved, accessible
- Red Wing Hiking Trail - 0.65 mile. Easy, located in campground
Visitors may also hike down to the canal feeder junction near the historic Miami and Erie Canal to the Miami-Erie Trail, Buckeye Trail, and North Country Scenic Trail.
Under the proper conditions, park visitors can enjoy snowmobiling, ice fishing, and cross-country skiing.
More to Do
- Seasonal naturalist programming
- Neil Armstrong Air and Space Museum
- Baker Woods and Gross Woods state nature preserves
- Mercer Wildlife Area
- Local events may also be found at Wapokeneta Chamber of Commerce
History & Natural Features
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 his 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 5-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, the 13,500-acre Grand Lake was the largest man-made lake in the world. The lake was connected to the canal by a 3-mile feeder.
The canal prospered until the advent 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 Ohio were the first areas to be dedicated as state parks in 1949.
At one time, the vast expanse of water that is Grand Lake St. Marys, was a vast wet prairie and forests, which stretched from the Allegheny mountains of Pennsylvania to the prairies of Illinois. In addition to forests, pre-settlement Ohio harbored large prairies and wetlands. Today, the park contains varying habitats including woodlands, wetlands, and prairies in addition to surrounding croplands.
Grand Lake St. Marys was the site of the first offshore oil drilling in the world. Between 1891 and about 1913, more than 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.
Perfect for bird enthusiasts, Grand Lake St. Marys lies along one of the country's major migration routes. Many birds use the lake as a resting stop and nesting area, including Canada geese, ducks, grebes, swans, egrets, loons, herons, cormorants, and ospreys. Bald eagles, magnificent birds long absent from the area, have begun nesting 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.