Mercer, PA

Mercer is a borough in Mercer County, Pennsylvania, United States. The population was 9,924 at the 2010 census. It is part of the Youngstown- Warren-Boardman, OH-PA Metropolitan Statistical Area.

The borough was founded in 1792 and named for William Mercer, 1st Earl of Macartney, an English diplomat who served as Secretary of State for the Southern Department from 1768 to 1772 and as Ambassador to France from 1772 to 1775. The borough's first settler was Ebenezer Haines.

Mercer is located at (40.527691, -80.819388). It is bordered by West Middlesex Township to the north and east, North Huntingdon Township to the south and west, and East Huntingdon Township to the northwest. Interstate 79 passes through the borough just east of its center; I-79 leads northeastward into Ohio and southwestward into West Virginia. According to the United States Census Bureau, Mercer has a total area of , all land.

As of the census of 2000, there were 8,898 people, 3,477 households, and 2,422 families residing in the borough. The population density was 2,711 people per square mile (1,099/km²). There were 3,.