Mercer County. Formed March 12, 1800 from Allegheny County. The U.S. census reported 3228 residents in 1800. Named for General Hugh Mercer, Revolutionary hero killed at Battle of Princeton, 1777. Early iron and coal center. Mercer, the county seat, was incorporated 1814.

N Diamond St. at N side of Co courthouse, at Courthouse Square, Mercer, PA, United States

General Hugh Mercer - PLAQUE. In memory of General Hugh Mercer. Born in Scotland, Colonel on General Forbes Expedition against Fort Duquesne 1758, Commander at Fort Pitt 1759, Colonel 3rd Virginia Regiment 1776, Brigadier General Continental army 1776, killed in the Battle of Princeton 1777.

N Diamond St., N side of Co. courthouse, right column support, Mercer, PA, United States