West Middlesex, Pennsylvania  West Middlesex is a borough along the Shenango River in southwestern Mercer County, Pennsylvania, United States. The population was 863 at the 2010 Census. It is part of the Youngstown-Warren-Boardman, OH-PA Metropolitan Statistical Area. West Middlesex is located at (41.173630, -80.456874). According to the United States Census Bureau, the borough has a total area of . The Shenango River runs through West Middlesex, making it part of the Shenango Valley. West Middlesex is one of the oldest localities in Mercer County. Samuel Byers, Andrew Wylie, William Bell, Richard Vanfleet and several others arrived in the vicinity in the late 18th century. In 1787, James Gibson received a plot of land west of the Shenango River for military services. Shortly thereafter, ownership of that land passed to Jacob Edeburn. In 1818, Jacob's son William Edeburn built a log grist mill on part of the land. It was purchased by James McConnell in 1821, who built a log house nearby. In 1830, Edeburn built a sawmill, and McConnell built a flour mill. James Gilkey, cultivator of the "Neshannock potatoes," surveyed the site and platted the town in 1836 on McConnell's land. A store and a tavern were opened about the time the town was platted, and in 1840 the post office was established, with Robert Young as the first postmaster. In 1864 West Middlesex was incorporated as a borough. The first burgess was D. Edeburn, and the first members of the council were C.W. Watson, Hiram Veach and G.R. Tuttle. West Middlesex was one of the first places in the Shenango Valley to become a center of the iron business. The old Middlesex furnace, erected in 1845, was a charcoal-burning plant. Additional coke and ore furnaces followed, including the Fannie (1873, remodeled in 1885) and the Ella (1882). As of the census of 2010, there were 863 people, 368 households, and 244 families residing in the borough. The racial makeup of the borough was 96.9% White, 1.2% African American, 0.3% Asian, 0.6% from other races, and 1.0% from two or more races. Hispanic or Latino of any race were 0.3% of the population.