On February 12, 1820, the Ohio government authorized the creation of Mercer County. Residents named the county in honor of General Hugh Mercer, a hero of the American Revolution. In 1791, Indians defeated General Arthur St. Clair’s army along the Wabash River.

Grand Lake St. Mary’s came into being as a reservoir to supply water for the Miami and Erie Canal. It was begun in 1837, long before mechanized equipment. It was constructed by 1,700 men, mostly Irish and German immigrants, yielding axes and shovels from sunrise to sunset. Their wages came to a paltry 30 cents a day and a jigger of whisky. The whisky was relied upon to combat malaria. The 17,500 acre lake was completed in 1845 at a cost of $600,000 and was, for many years, the largest artificial body of water in the world. It is still the largest artificial body of water in the world built without the use of machinery.

Early settlers were mostly of English, Irish and French heritage. Most people of the county depended on farming but there were several tire and bicycle plants around. The completion of the canal and its fee-reservoir also made a vast difference in living costs. The canal did a thriving business until it was supplanted by the railroads in the late 1860’s.

In 1888 and 1889, oil was discovered in the St. Mary’s area and many wells were drilled during the oil boom that followed. Some of those wells were drilled in Grand Lake St. Mary’s, whose surface was once studded with derricks.

Mercer County has one city, Celina, which was platted in 1834, and has a population of over 10,000 residents. Celina serves as the county seat. Our eight villages are: Burkettsville, Chickasaw, Coldwater, Ft. Recovery, Mendon, Montezuma, Rockford and St. Henry.