(6-15-20) Grand Lake St. Marys is west of St. Marys, and south-east of Celina  in the north-western part of Ohio. 3/4th of the lake is in Mercer County and a large part of the shore line is located in the city limits of Celina…not St. Marys.

Grand Lake St. Marys was constructed in the early 19th century as a reservoir for the Miami and Erie Canal, which connected the Ohio River with Lake Erie. At one time the lake was the world’s largest man-made lake. The canal system thrived for about thirty years in the mid-to-late 19th century before it was replaced by the railroads. In the 1890s oil was discovered in the area, and oil derricks were set up in the lake sometime around 1891. This made Grand Lake the location for the first off shore oil drilling to take place. The lake became one of Ohio’s first state parks in 1949 with recreational facilities built in the following years.

Over the years residents from Celina and St. Marys still talk about the naming of the lake.

grand lake map

Above map from United States Geological Survey Board of Geographic Names in 2020

The official geographic name of the lake is Grand Lake. The United States Geological Survey Board of Geographic Names disapproved a proposal to change the name Grand Lake to Grand Lake-Saint Marys, which is the name given on state maps and documents.

Although the lakeimprovement.com site disagrees with this –

After decades of debate, the moniker Grand Lake St. Marys was officially recognized by the U.S. Geographic Survey and the State of Ohio

On the Southern Yankee: A Writer’s Log from 2013 –

Officially named Grand Lake in the US Geographical Survey, it is known locally as Grand Lake Saint Marys—a moniker that has stirred no little jealously and debate between the lake-front cities of Saint Marys and Celina—and that’s even the name posted on Ohio road signs, including those on Interstate 75 and US 33, despite the Federal government’s refusal to add the Saint Marys suffix to official maps.

So why is it called Grand Lake St. Marys some reasons from lakeimprovement.com?

  • What’s in a name? For decades the local lake community has battled over the official name of Grand Lake St. Marys – so much so that The Evening Leader even once threatened to sue The Daily Standard over the matter!
  • A war of words. The lake has been called Lake Mercer, Lake St. Marys, Mercer Reservoir, Grand Reservoir, Grand Lake, Lake Celina, and, of course, Grand Lake St. Marys.
  • The original name? The lake was originally called Lake Mercer, or the Mercer Reservoir. At that time Auglaize County (on the east side of the lake today) did not exist. St. Marys was in Mercer County, and served as the County Seat. In 1848, Auglaize County was carved out of Mercer and Allen counties.

March 23rd, 1907 – Celina Advocate

Lake Mercer

The 1920 edition of the Encyclopædia Britannica shows the name as Lake Mercer on the map of Ohio in the article on Ohio. “Lake St. Marys” was a name introduced in the early 1900s and wasn’t popular with Celina residents. The body of water has also been referred to as “Grand Reservoir” and “Lake Celina” among other names.

grand lake standard

So what should the name be?

Over the years a story has been passed down that a meeting actually happened between the two towns and the Celina Representatives left drunk and gave away the name to St. Marys? Why not just Grand Lake? Is St. Marys till upset that in the 1800’s they were booted from Mercer County and Celina became the new county seat, replacing St. Marys and Wapakoneta was selected as the Auglaize County seat?