All 400-Series Area Codes
Browse every active area code in the 400–499 range across the United States.
The 400-series is a tighter block than its neighbors, with several codes reserved for non-US or non-geographic use and therefore absent from this listing. The codes that remain anchor a genuinely diverse set of metros — 404 in Atlanta, 415 in San Francisco, 410 in Baltimore, 412 in Pittsburgh, 408 in San Jose, and 480 in Mesa, Arizona. One quirk worth noting: three different Springfields fall inside this range — 413 in Massachusetts, 417 in Missouri, and 447 in Illinois — a reminder that area codes are tied to specific cities, not city names. Several major metros also appear with both an original code and a later overlay, including Atlanta (404 and 470), Baltimore (410 and 443), and Los Angeles (424, alongside its 3xx-series codes), with the overlays added as number demand outpaced the original allocations.
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