Area code 878 is an overlay for both 412 and 724 in southwestern Pennsylvania, including the city of Pittsburgh and surrounding suburbs. It was implemented in 2001 to accommodate number exhaustion in a region that blends industrial heritage with modern tech and healthcare growth. Pittsburgh, the anchor city, is known for its transformation from steel to innovation, with strong sectors in robotics, AI, education, and medicine. Carnegie Mellon University and the University of Pittsburgh are major research centers, while companies like UPMC and PNC Bank also call the city home. While 412 remains the legacy area code most tied to Pittsburgh, 878 functions across the same geographic range and is regularly assigned to new phone lines. A number in 878 still conveys Pittsburgh roots, and it ensures continuity and capacity for businesses serving the greater metropolitan area.