Area codes in Union City, California
Union City, California uses 2 area codes — 510 and 341. The main Union City area code is 510.
Area codes serving Union City
Phone numbers in Union City are written as ten digits — for example (510) 555-0190 — and fall in the Pacific Time zone.
How Union City came to have 2 area codes
The original Union City area code is 510, in service since 1991. As the area ran low on available numbers, an overlay code was added over the same region for new phone lines: 341 (2019). Existing numbers kept their original code — an overlay never forces anyone to change their number — which is why Union City now uses all 2 codes and every local call is dialed with ten digits.
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More cities in California
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- San Diego area codes
- San Francisco area codes
- Sacramento area codes
- San Jose area codes
- Fresno area codes
- Long Beach area codes
- Oakland area codes
Frequently asked questions
What is the area code for Union City?
The main area code for Union City, California is 510. Union City is now served by 2 area codes in total: 510, 341.
How many area codes does Union City have?
Union City has 2 area codes: 510, 341.
Why does Union City have more than one area code?
As Union City used up the numbers available in its original area code (510, in service since 1991), additional "overlay" codes were added over the same area so new phone numbers could keep being assigned.
How do you dial a Union City number?
Dial all 10 digits — the area code (510 or 341) followed by the 7-digit local number. From abroad, dial +1, then the area code and number.
Sourced from the official NANPA (North American Numbering Plan Administrator) numbering database, current as of August 2, 2026. Refreshed monthly.