Harmarville, Pennsylvania is an unincorporated community located in Harmar Township, Allegheny County, Pennsylvania. In Law, an unincorporated area is a region of land that is not a part of any Municipality. Harmar Township is a township in Allegheny County, Pennsylvania, United States. Allegheny County is a County in the southwestern part of the U Although it is not tracked by the U.S. Census, the population is estimated to be 1,200 residents. The United States Census is a decennial Census mandated by the United States Constitution.