Area code 878 is an overlay for both area codes 412 and 724 in western Pennsylvania, including the Pittsburgh metro area and surrounding suburbs. Introduced in 2001, it was one of the first overlays in the U.S. to span two area codes, necessitating ten-digit dialing throughout the region. The 878 area supports the growing demand for phone numbers due to increased mobile usage and business expansion. While 412 and 724 remain legacy codes, 878 is commonly used for new numbers in both urban and suburban areas. The region is known for its steel industry heritage, tech innovation, and vibrant cultural scene. 878 is integral to modern telecommunications in the greater Pittsburgh region.