What is what area code is 510?

The area code 510 serves the northwestern portion of the East%20Bay region of the San%20Francisco%20Bay%20Area in California. It primarily covers cities in Alameda%20County and Contra%20Costa%20County. Some of the major cities within the 510 area code include Oakland, Berkeley, Fremont, and Hayward. It was created in 1991 when it was split from area code 415. Due to the increasing demand for phone numbers, it has been overlaid with area code 341 in certain regions.