About Area Code 423
- Region Code
- 423
- City
- Chattanooga
- State
- Tennessee
- Largest City
- Chattanooga
- Neighboring Codes
- Time Zone
- Eastern Time
Tennessee
(423) Area Code 423 — Chattanooga, Tennessee
423 Area Code – Chattanooga, Tennessee: Location, Time Zone & History
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Map of Area Code 423
Available Phone Numbers
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History & Cultural Notes
Few U.S. area codes are geographically split in two, but 423 is one of them: it covers two separate sections of East Tennessee, the Chattanooga and Cleveland area on one side and the Tri-Cities and Morristown area on the other, divided by the territory of area code 865 around Knoxville. That unusual shape is a direct result of how the code evolved over time rather than any original design.
Area code 423 was created on September 11, 1995, when it split off from 615 and took over eastern Tennessee, including Knoxville, Chattanooga, and the Tri-Cities. That arrangement did not last long; in 1999, Knoxville and most of central East Tennessee were carved out into the new code 865, leaving the remaining 423 territory as the two non-contiguous sections it forms today. More recently, growing demand led Tennessee regulators to approve an all-services overlay, 729, on May 30, 2023, and mandatory ten-digit local dialing took effect across the region on August 5, 2025 ahead of the overlay code becoming available for assignment the following month.
The region's economy spans healthcare, manufacturing, logistics and transportation, tourism, and insurance and financial services, with communities including Johnson City, Kingsport, Bristol, Cleveland, and Morristown served alongside Chattanooga.