Coraopolis is a borough in Allegheny County, Pennsylvania, United States. The population was 5,677 at the 2010 census. In 1940 the population peaked at 11,086. It is a small community located to the west of Pittsburgh, along the Ohio River and to the east of the Pittsburgh International Airport. The borough is noted for its steep topography, numerous brick streets and many large, old homes. The American Bridge Company is headquartered in Coraopolis.