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

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.

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.

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 during the War of 1812, and some of his 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.

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.

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