Grand Lake Saint Marys State Park is an Ohio state park, west of St. Marys

St. Marys, Ohio

St. Marys is a city in Auglaize County, Ohio, United States. The population was 8,342 at the 2000 census. It is included in the Wapakoneta, Ohio, Micropolitan Statistical Area.-History:...

, and south-east of Celina

Celina, Ohio

Celina is a city in and the county seat of Mercer County, Ohio, United States. The population was 10,303 at the 2000 census. Celina is situated on the western shores of Grand Lake St. Marys.-History:...

, 23 miles (37 km) south-west of Lima

Lima, Ohio

Lima is a city in and the county seat of Allen County, Ohio, United States. The municipality is located in northwestern Ohio along Interstate 75 approximately north of Dayton and south-southwest of Toledo....

 in the north-western part of the U.S. state

U.S. state

A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

 of Ohio

Ohio

Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...

.

Grand Lake covers 13500 acres (5,463.3 ha) in Mercer

Mercer County, Ohio

Mercer County is a county located in the state of Ohio, United States. Its county seat is Celina and is named for Hugh Mercer, an officer in the American Revolutionary War.The Celina Micropolitan Statistical Area includes all of Mercer County.-Geography:...

 and Auglaize

Auglaize County, Ohio

As of the census of 2000, there were 46,611 people, 17,376 households, and 12,771 families residing in the county. The population density was 116 people per square mile . There were 18,470 housing units at an average density of 46 per square mile...

 counties. Grand Lake is the largest inland lake in Ohio in terms of land area, but is extremely shallow, with an average depth of only 5 to 7 ft (1.5 to 2.1 ).

The park is open for year round recreation including boating, fishing, swimming and hunting.