Area Codes
| 423 | Tennessee (Two disconnected portions of East Tennessee-Bristol, Johnson City, Kingsport in north; Chattanooga, Cleveland in south), split from 615 | More information at: Area Code 423 Phone Number Blocks
| 423 | Tennessee (Two disconnected portions of East Tennessee-Bristol, Johnson City, Kingsport in north; Chattanooga, Cleveland in south), split from 615 | More information at: Area Code 423 Phone Number Blocks