Named for General Hugh Mercer, a distinguished officer of the Revolution, Mercer County was established in 1820 by a legislative act creating counties from land in Ohio ceded by the Indians. Its original configuration included the western part of Auglaize, and Darke County administered it until 1824, when the seat of justice was established in St. Marys; the county seat moved to Celina in 1839. In 1848, the county’s eastern portion was used to form part of Auglaize County. General St. Clair’s military march, ending with his army’s rout at Ft. Recovery in 1792, and the subsequent expedition of Gen. Mad Anthony Wayne marked the area’s transition from Indian lands to American frontier lands. As forts were built across the Indiana and Ohio territories, surveyors studied and evaluated the countryside. In 1810, Capt. James Riley, a surveyor, wrote to B. Sanford, Esq. that along the banks of streams and rivers the land was good and dry and each quarter section could support a good farm; he praised the region’s timber and underbrush, while noting swamps and wet prairies away from the waterways. He also wrote that the section’s climate, soil, local situation, arts, sciences, and commerce promised great importance within a few years. Riley’s letters show that he was chiefly concerned with possible canal routes linking Lake Erie streams with the Ohio and Mississippi river systems and with their effect on the territory’s development. His prediction was borne out as the Miami and Erie Canal system helped make the area one of the state’s most productive agricultural regions.