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The 559 Secret: Everything You Need To Know About Hanford, CA's Area Code (and The New 357 Update)

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As of today, Thursday, December 25, 2025, the primary telephone area code serving Hanford, California, is 559. However, the telecommunications landscape in the Central Valley has recently undergone a significant and mandatory change that every resident and business owner in Kings County needs to be aware of: the introduction of the 357 area code. This new addition has created an "overlay complex" with the existing 559 code, meaning new phone lines in the region may be assigned either 559 or 357, and all local calls now require 10-digit dialing to connect. This shift from a single area code to an overlay complex is a direct response to the explosive demand for new telephone numbers in the rapidly growing San Joaquin Valley region. The 559 area code, which has served the area since 1998, was projected to exhaust its available number pool, prompting the California Public Utilities Commission (CPUC) to approve the new 357 code. Understanding this overlay is essential for seamless communication, whether you are a long-time resident of Hanford, a new arrival, or a business operating in the wider Central Valley region.

The New Reality: Understanding the 559/357 Overlay Complex

The most critical piece of information for anyone dealing with phone numbers in Hanford is the implementation of the 559/357 overlay. This is not a split, where a geographic boundary is drawn, but an overlay, where two area codes serve the exact same geographic region.

Why the 357 Area Code Was Added

The 559 area code was projected to run out of available prefixes—the first three digits of a seven-digit phone number—due to the proliferation of mobile phones, VoIP lines, and fax machines, alongside population growth in cities like Fresno, Visalia, and Hanford. To ensure a continuous supply of new telephone numbers without disrupting existing service, the North American Numbering Plan Administrator (NANPA) and the CPUC introduced the 357 area code. This overlay was officially implemented in 2025, making any information about the 559 area code incomplete without mentioning its new companion, 357.

The Mandatory Shift to 10-Digit Dialing

With the introduction of the 357 overlay, 10-digit dialing became mandatory across the entire 559/357 service area. This means:
  • Local Calls: To dial any number, even if it is right next door in Hanford or in a nearby community like Lemoore or Corcoran, you must dial the full 10 digits (Area Code + 7-digit number).
  • New Numbers: New telephone lines and services activated after the overlay date are now being assigned numbers with either the 559 or the 357 area code.
  • Existing Numbers: All existing 559 numbers remain the same and do not need to be changed.
This change affects not just phone calls but also programmed devices. Residents and businesses must update their security systems, life safety systems, PBXs, fax machines, and any other equipment that stores 7-digit local numbers to include the area code.

Hanford's Area Code History: From 209 to 559

Hanford’s current area code, 559, is relatively young in the history of the North American Numbering Plan (NANP). Its existence is a direct result of the rapid expansion of telecommunications in the late 20th century, which necessitated the splitting of larger, original area codes.

The Great Split of 1998

Prior to 1998, Hanford and the entire surrounding Central Valley were part of the much larger 209 area code. The 209 code, one of the original 86 area codes established in 1947, covered a vast stretch of California, from the San Joaquin Valley up to the Sierra Nevada foothills. By the mid-1990s, the population boom and the explosion of telecommunication devices led to a critical shortage of available numbers in the 209 region. To solve this issue, the 209 area was geographically split. The southern and central portions, including Kings County, Fresno County, and Tulare County, were assigned the new 559 area code, which was placed in service in 1998. The 209 area code continued to serve the northern San Joaquin Valley, including cities like Stockton and Modesto. This history explains why some older businesses or long-time residents may still occasionally reference the 209 code when discussing the region's past, but 559 has been the standard for over two decades.

Geographic Footprint: Where 559 and 357 Reign Supreme

Hanford is the most populous city and the county seat of Kings County. The 559/357 area code complex is the sole area code for all of Kings County, covering not just Hanford but also neighboring communities such as Lemoore, Corcoran, and Avenal.

The Six-County Reach of the Central Valley Area Code

The 559/357 service area is a vast, six-county region that forms the heart of California’s agricultural powerhouse, the Central Valley. This extensive area includes all or portions of the following counties and their major cities:
  • Fresno County: Home to the city of Fresno and Clovis.
  • Kings County: Home to Hanford and Lemoore.
  • Tulare County: Home to Visalia and Tulare.
  • Madera County: Including the city of Madera.
  • Merced County: A small portion is included.
  • Mariposa County: A small portion is included.
This wide geographic scope means that many local calls within the Central Valley, such as a call from Hanford to Fresno, are considered local calls but still require 10-digit dialing due to the overlay. The area code serves a diverse mix of urban centers, expansive agricultural lands, and smaller farming communities, making it a vital telecommunications zone for a significant portion of California’s economy.

Essential Telecommunications Entities in the 559/357 Region

For residents and businesses in Hanford, several other key entities and numbers are essential for daily life and commerce. Understanding these related codes provides a complete picture of the area's numbering infrastructure.

Hanford ZIP Codes

While the area code is for phone service, the ZIP Codes (Zone Improvement Plan Codes) are used for mail delivery and geographic identification. Hanford is primarily served by two main ZIP Codes: 93230 and 93232. The 93232 code is often used for P.O. Boxes, while 93230 covers the main residential and business areas of the city.

The Future of Numbering in the Central Valley

The introduction of the 357 overlay is expected to provide a sufficient supply of new telephone numbers for the Central Valley for several years to come. This proactive measure by the CPUC ensures that the region’s growing population and expanding economy—driven by agriculture, education, and commerce—will not face a shortage of essential communication resources. As the 559 and 357 area codes coexist, the only lasting change for users is the permanent requirement to dial all ten digits for every local call, a small adaptation for the long-term stability of the region’s telephone numbering system.
The 559 Secret: Everything You Need to Know About Hanford, CA's Area Code (and the New 357 Update)
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