Area code 484 is an overlay for southeastern Pennsylvania, covering the same region as area code 610, including cities like Allentown, Reading, West Chester, and Bethlehem. It was introduced in 1999 due to the high demand for new phone numbers in the Philadelphia suburbs and Lehigh Valley area. Ten-digit dialing became mandatory with the overlay. While 610 is often seen as the legacy code, 484 is now widely used for mobile phones and newer business lines. The area is known for its mix of suburban living, historical towns, and strong educational and healthcare institutions. 484 plays a key role in the continued development of this growing part of Pennsylvania.