The 408 area code is an essential part of California's telecommunications network, serving the southern part of the San Francisco Bay Area.

Establishment and Geographic Coverage: The 408 area code was created on January 1, 1959, as a split from the 415 area code. It primarily serves the Santa Clara Valley, including major cities like San Jose (which is the largest city in the area code), Santa Clara, and Sunnyvale, along with surrounding communities in Silicon Valley.

Economic and Cultural Importance: The region covered by the 408 area code is globally recognized as the heart of Silicon Valley, a major hub of technology and innovation. This area is home to many high-tech corporations and startups, playing a crucial role in the global technology industry. The area code supports a dynamic economy that includes technology, engineering, and computer science sectors, as well as world-renowned research institutions and universities.

Introduction of Overlay Area Code and Ten-Digit Dialing: To address the need for more telephone numbers, the 669 area code was introduced as an overlay to the 408 area code on November 20, 2012. With this overlay, ten-digit dialing (area code + phone number) became mandatory for all local calls within the 408 and 669 area codes. This change was a significant adaptation in dialing practices, reflecting the region's continuous growth and technological development.

These facts about the 408 area code underscore its critical role in supporting the telecommunications needs of the Santa Clara Valley and Silicon Valley. The area code, along with its overlay 669, ensures efficient connectivity for a region known for its economic importance and technological innovation.