From Ohio History Central
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. Once whites began to migrate to the area and canal construction began, the Miami and Erie Canal flowed through the county. To provide the canal with a water source, workers constructed Lake St. Marys in 1837. It was the largest man-made lake in the world at this time. Today, the lake is a major tourist attraction.
Mercer County is located in the northwestern part of Ohio. Its western border helps form the boundary between Ohio and Indiana. The county seat is Celina, which is the largest city in the county with a population of 10,303 people in 2000. Approximately eighty-eight percent of Mercer County�s 463 square miles are covered in farms. Only 1.4 percent of the county is deemed to be urban. The county averages eighty-eight people living in each square mile. Between 1995 and 2000, the county experienced a 3.8 percent increase in population. This is unusual for Ohio�s more rural counties, as residents seek better opportunities in the state�s larger cities. In 2000, the county�s residents numbered 40,924 people.
Most of Mercer County�s residents find employment in agricultural positions. In the state, the county ranks first in hog raising, second in corn production, and third in cattle raising. Retail, manufacturing, and government positions finish second, third, and fourth respectively. In 1999, the county�s per capita income was 23,376 dollars, with 6.5 percent of the county�s residents living below the poverty level.
Most voters in Mercer County claim to be independents, yet in recent years, they have overwhelmingly supported Republican Party candidates at the national level.