Send To A Friend

Boating Links

Grand Lake St. Marys

Originally constructed as a feeder reservoir for the Miami-Erie Canal, Grand Lake St. Marys is the largest inland lake in Ohio. It is approximately 9 miles long and 3 miles wide boasting 52 miles of shoreline covering an area of more than 12,900 acres. Three lighthouses stand guard around the lake. The oldest was erected in 1923 and the newest in 2003.

Grand Lake Saint Marys State Park is open for year-round boating, hunting, fishing, swimming and picnics.The campground offers a nature center and a boat ramp with overnight courtesy docks.

Ohio's only airport for seaplanes is on The Grand Lake St. Marys Seaplane Base.


Year-round fishing attracts fishermen and women throughout the seasons. The lake is populated with largemouth bass, white and black crappies, bluegills, walleye, channel and flathead catfish, yellow perch, bullheads, carp and suckers. Gizzard shad is the primary forage species. Grand Lake St. Marys offers handicap-accessible shoreline fishing piers.

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 which produces stock for Ohio's public fishing waters.


Search Grand Lake St. Marys Resources
    Grand Lake St. Marys OH Coordinates:
40.5427N, -84.4648W
Map It:
Lake Type:
Surface Area:
12,900 acres
Maximum Depth:
7 ft
869 ft
Normal Water Clarity:
1 ft
Major City:
Fort Wayne


The ODNR Division of Parks & Recreation operates and maintains seven boat ramps. Boats and seasonal docks can be rented at the marina.

Open to boats of all types there is no horsepower limit on Grand Lake St. Marys. There is, however, a 300 ft no-wake zone enforced along the entire shore. Travel restrictions prohibit boats from entering the state wildlife refuge found at the southwest corner of the lake.


Grand Lake St. Marys provides seven air-conditioned rental cabins. Two small, two modern and three large cabins can be rented from May to October.

The campground has 216 campsites with more than 135 equipped with electricity.

Please review the Lake Resource Guide for additional lodging in the area.


Grand Lake St. Marys is located in west central Ohio near the Indiana border in Mercer and Auglaize counties. The city of St. Marys is located near the northeast corner of the lake and Celina is on the northwest corner. It is 23 miles south-west of Lima.

The Neil Armstrong Air and Space Museum is located in nearby Wapakoneta. Other nearby towns: Spencerville, Coldwater and Fort Recovery.

Fun times at Grand Lake St. Marys Grand Lake St. Marys

Grand Lake St. Marys Grand Lake St. Marys

Average Temperatures Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Avg. High  33 Avg. High  38 Avg. High  49 Avg. High  62 Avg. High  72 Avg. High  81 Avg. High  84 Avg. High  82 Avg. High  76 Avg. High  64 Avg. High  50 Avg. High  37
Avg. Low  19 Avg. Low  22 Avg. Low  30 Avg. Low  41 Avg. Low  51 Avg. Low  61 Avg. Low  64 Avg. Low  62 Avg. Low  55 Avg. Low  44 Avg. Low  35 Avg. Low  24