Area Code 423

Tennessee

Area code 423 serves Tennessee, primarily Chattanooga, in the Central Time (CT) time zone. It has served the region since 11-Sep-1995.

Published: Updated:

Overlay Area Code

This area code is part of an overlay region, meaning the same geographic area is served by multiple area codes. Overlay codes were introduced to meet growing demand for phone numbers without requiring existing customers to change their numbers.

This area code shares its geographic region with: area code 729 (Chattanooga).

In service since: 11-Sep-1995

Learn more about overlay and split area codes →

Area Code Splits

Parts of this area code’s original geographic region were later assigned new area codes through splits. When a split occurs, some customers in the original area code region are assigned the new area code.

Split into: area code 865 (Knoxville).

Learn more about overlay and split area codes →

Demographics & Economics

Total Population
2,359,591
Population Density
115 people/sq mi
above U.S. average (U.S.: 93 people/sq mi)
Median Household Income
$57,408
below U.S. median (U.S.: $75,144)
Poverty Rate
16.0%
above U.S. average (U.S.: 11.5%)
Unemployment Rate
5.4%
above U.S. average (U.S.: 3.6%)
Education Attainment
Bachelor's Degree+
23.0%
below U.S. average (U.S.: 33.7%)
High School or Lower
40.2%

Statistics are population-weighted aggregations from Census ACS 5-year estimates. Population figures are approximate — see Sources & Methodology for details on how area code populations are derived.

See how this area code compares to all US area codes in the Statistics dashboard.

Time Zones

  • Central Time (CT)
  • Eastern Time (ET)

NANPA Relief Status

According to the latest NANPA analysis (July 2026), this area code is not currently listed as exhausting within the next 36 months. No relief planning is in progress for this NPA.

Source: NANPA NPA Relief Planning Reports · See all relief planning statuses

Current Time

Central Time (CT)
 
 
Eastern Time (ET)
 
 

This area code spans multiple time zones.

Prefix Utilization

Geographic Coverage

State

TN

Major Cities

  • Chattanooga
  • Johnson City
  • Kingsport
  • Cleveland
  • Morristown
  • Bristol
  • East Ridge
  • Greeneville
  • Elizabethton
  • Athens
  • Soddy-Daisy
  • Red Bank
  • Middle Valley
  • Collegedale
  • Signal Mountain
  • Bloomingdale
  • Harrison
  • South Cleveland
  • La Follette
  • Dayton
  • Church Hill
  • Newport
  • Sweetwater
  • Jonesborough

and 108 more cities

Area Code 423 geographic coverage map (light mode)

Historical Timeline of Area Code 423

On September 11, 1995, area code 423 entered service as Tennessee's first new area code in 41 years. BellSouth Telecommunications filed IL94/11-018 to split the 615 NPA, citing substantial telephone number growth across central and eastern Tennessee. Nashville retained 615; the eastern portion covering Chattanooga, Knoxville, and the Tri-Cities transferred to the new 423 NPA. Source: Wikipedia.

Key milestones:

  • 1947: Tennessee established as a single NPA with area code 901, one of the original 86 area codes in the North American Numbering Plan.
  • 1954: Area code 901 was reduced to West Tennessee; the remainder of the state received area code 615.
  • 1995: Area code 423 created September 11 following BellSouth's 1994 filing (IL94/11-018). Covered Chattanooga, Knoxville, Tri-Cities, and all of East Tennessee. Permissive dialing continued until February 26, 1996. Source: Wikipedia
  • 1999: Area code 865 created November 1, splitting off from 423 for Knoxville and central East Tennessee. The code 865 was chosen to spell "VOL" on a telephone keypad in honor of the University of Tennessee Volunteers. This split created the rare non-contiguous geometry of 423. Source: Wikipedia
  • 2002: Number pooling implemented in the southern 423 region (Chattanooga area), extending the projected number exhaustion timeline.
  • 2023: Tennessee PUC approved an all-services overlay of 423 with new area code 729 under Docket No. 22-00128 (May 30, 2023). NANPA issued planning letter PL-619.
  • 2024: Permissive 10-digit dialing began August 5, 2024.
  • 2025: Mandatory 10-digit dialing begins August 5, 2025. Area code 729 in-service date September 5, 2025.

Regulatory History

Area code 423 has been managed through Tennessee PUC proceedings and NANPA planning letters over three decades. The regulatory actions reflect the transition from number exhaustion relief to proactive conservation measures. Source: NANPA PL-619

YearEventDocketRegulatory Action & Impact
1994615 split filingIL94/11-018BellSouth Telecommunications filed with NANPA to split the 615 NPA due to number exhaustion in East Tennessee. The filing initiated the process that would create area code 423 for the eastern portion of the state.
1995423 split effectiveIL94/11-018Area code 423 activated September 11, 1995. Permissive 7/10-digit dialing permitted through February 26, 1996, allowing callers to use either 7 or 10 digits during the transition period.
1999865 split from 423NANP183FCC approved creation of area code 865 for the Knoxville region under NANP183. The code 865 was selected to spell "VOL" on a telephone keypad. This split created the rare non-contiguous geometry of 423.
2002Number pooling—Number pooling implemented in southern 423 (Chattanooga area), extending projected number exhaustion to 2025.
2023729 overlay approved22-00128Tennessee PUC approved all-services overlay of 423 with area code 729 (May 30, 2023). NANPA issued planning letter PL-619.
2024Permissive 10-digit dialingPL-629Permissive 10-digit dialing began August 5, 2024, as part of the 729 overlay transition. NANPA PL-629 superseded PL-619 with revised dates.
2025Mandatory 10-digit dialingPL-629Mandatory 10-digit dialing effective August 5, 2025. 729 in-service date September 5, 2025, when 423 codes are exhausted.

County Coverage

Population-weighted county share based on aggregated ZCTA population (100% = total mapped population for area code 423).

CountyPopulationShare
Hamilton, TN418,15117.7%
Sullivan, TN217,8919.2%
Washington, TN192,2828.1%
Hawkins, TN126,2415.4%
Carter, TN124,2815.3%
Bradley, TN120,8855.1%
McMinn, TN98,6174.2%
Unicoi, TN94,6814.0%
Bledsoe, TN90,3923.8%
Greene, TN84,3663.6%
Sequatchie, TN71,2803.0%
Marion, TN68,9472.9%
Cocke, TN67,2022.8%
Hamblen, TN66,0802.8%
Monroe, TN55,7712.4%
Polk, TN55,2662.3%
Campbell, TN47,1802.0%
Rhea, TN40,1791.7%
Jefferson, TN39,5921.7%
Claiborne, TN38,9061.6%
Scott, TN25,7241.1%
Van Buren, TN24,1601.0%
Meigs, TN23,8011.0%
Loudon, TN22,7601.0%
Roane, TN20,5740.9%
Johnson, TN19,2420.8%
Morgan, TN19,0650.8%
Hancock, TN18,3240.8%
Scott, VA14,4910.6%
Cumberland, TN13,0120.6%
Union, TN12,4490.5%
Sevier, TN7,4300.3%
Franklin, TN6,6040.3%
Lee, VA6,1600.3%
Grainger, TN4,1560.2%
Fentress, TN2,3130.1%
Anderson, TN1,1360.0%

Area Code 423 Family Tree

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615423629931729865
3
Total Codes
1
Splits
1
Overlays
1
Max Depth

All Descendants

Code ▲StateType In Service Parent
729TNoverlay05-Sep-2025423
865TNsplit01-Nov-1999423

Area code 423 was originally assigned in 11-Sep-1995 to serve TN. Over the years, it has generated 2 descendant area codes through a combination of geographic splits and overlays as demand for telephone numbers grew.

Call Context

Metropolitan area

This area code covers a metropolitan region in TN with moderate to high population density, centered on Chattanooga and surrounding communities.

Nearby Area Codes

Area codes geographically closest to 423.

Area code 865 map card showing Knoxville (light mode)
865TNKnoxvilleEastern Time (ET)Split
Area code 828 map card showing Asheville (light mode)
828NCAshevilleEastern Time (ET)Split
Area code 821 map card showing Greenville (light mode)
821SCGreenvilleEastern Time (ET)Overlay
Area code 864 map card showing Greenville (light mode)
864SCGreenvilleEastern Time (ET)Geographic

Other Area Codes in Tennessee

Area codes that also serve Tennessee, linked for easy comparison.