Carnegie is a borough in Allegheny County, Pennsylvania, United States and is part of the Pittsburgh Metro Area. The population was 7,972 at the 2010 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 833 ft (254 m) above sea level. Carnegie is named after Andrew Carnegie, who donated one of his libraries for the gesture. It was incorporated on March 1, 1894. from the boroughs of Chartiers and Mansfield (separated by Chartiers Creek). Later, the borough annexed part of Robinson Township (now Rosslyn Heights). Neighborhoods include Rosslyn Heights, Cubbage Hill, Irishtown, Forsythe Hill, Library Hill, and Old Mansfield.