Vandergrift is a borough in Westmoreland County in the U.S. state of Pennsylvania, approximately northeast of Pittsburgh. Early in the 20th century, it had the largest sheet steel mill in the world. In July 1915, the borough of Vandergrift Heights was consolidated with Vandergrift. In 1900, 2,076 people lived here; in 1910, 3,876. The 1915 consolidation almost doubled the Vandergrift population when Vandergrift Heights added approximately 3,438 new residents (1910 population). By 1940, 10,725 people lived in Vandergrift. The population was 5,455 at the 2000 census, and 5,205 in 2010. Many of the exterior shots in the 2011 science-fiction film I am Number Four were filmed in Vandergrift, which was a stand-in for the fictional town of Paradise, Ohio.