Castle Shannon, PA
Castle Shannon is a borough in Allegheny County, Pennsylvania, United States and is part of the Pittsburgh Metro Area. The population was 8,556 at the 2000 census.
According to the United States Census Bureau, the borough has a total area of 1.6 square miles (4.1 km2), all of it land. Its average elevation is 1,040 feet (320 m) above sea level.
The first families settled Castle Shannon in 1786 in pursuit of farmland and timber. The most prominent farm was owned by David Strawbridge, which he named Castle Shanahan. Over time, the farm would lend its name to the area, as "Shanahan" would evolve into "Shannon."