Geographic Regions and Area Codes in Area Code 423

Area Code 423 is primarily situated in the state of Tennessee. It covers parts of East Tennessee, including the Tri-Cities region (Bristol, Johnson City, and Kingsport) and the city of Chattanooga. The area code spans 28 counties, including:

  • Hamilton County
  • Washington County
  • Sullivan County
  • McMinn County
  • Bradley County

Additionally, it serves 90 cities, with notable ones being Chattanooga, Johnson City, Kingsport, Cleveland, and Morristown. Due to the exhaustion of available numbers, an overlay area code, 729, has been introduced and will go into effect on August 5, 2024, with mandatory 10-digit dialing starting in early 2025.