Wilmerding is a borough in Allegheny County, Pennsylvania, United States. The population was 2,145 at the 2000 census. It is located 12 miles (19 km) southeast of Pittsburgh, Pa. At the start of the twentieth century, it had extensive foundries and machine shops of the Westinghouse Air Brake Company. In 1900, the population stood at 4,179 people; in 1910, it stood at 6,133. 5,662 residents were counted in 1940. Wilmerding is only a stone's throw from Turtle Creek, which takes its name from a small stream that flows past both places.