831 Area Code: California's Monterey Bay & Salinas Valley

Santa Cruz, Monterey, Salinas, and Watsonville all share the 831 area code, covering California's Central Coast from the Santa Cruz Mountains down through Big Sur. Carved out of San Jose's 408 on July 11, 1998, 831 has stayed a single, un-overlaid code ever since — a rare thing for California, and one that regulators don't expect to change anytime soon given the region's modest population.

This guide covers 831's counties and cities, what it does and doesn't reach, why its farmland-and-coastline economy keeps numbers in steady demand, and how to dial correctly.

Counties and cities at a glance

831 covers Monterey County, San Benito County, and Santa Cruz County in full — anchored by Santa Cruz, Monterey, Salinas, Watsonville, and Hollister, and stretching down the coast through Big Sur.

How 831 split from San Jose's 408

Rather than overlay the fast-growing South Bay, regulators chose a geographic split: 831 broke away from 408 on July 11, 1998, with a permissive dialing window that closed on February 21, 1999. Unlike 408 itself — which later added the 669 overlay as Silicon Valley kept growing — 831's population has stayed modest enough that a second code has never been needed.

An economy built on farmland and coastline

The 831 region runs on two industries that rarely sit this close together:

The Salad Bowl of the World The Salinas Valley supplies roughly 60% of the country's leaf lettuce and over half its celery, making agriculture Monterey County's single largest employer.

Coastal tourism The Monterey Bay Aquarium draws close to 2 million visitors a year, and Pebble Beach's golf courses and Big Sur's cliffside drives pull in visitors from around the world.

Silicon Valley overflow With San Jose's tech corridor just up the 408 corridor, many Bay Area professionals who work in tech but want coastal living end up here — the same kind of remote-first setup covered in 650, the Peninsula code just to the north. Many of these local businesses run their phones on UCaaS (Unified Communications as a Service), a single cloud platform for calling, video, and messaging that scales whether a company has one office or five. Contact us to set up an 831 number for your California business.

What 831 doesn't cover

831 stops well short of the South Bay: San Jose and the rest of Silicon Valley sit under 408 and 669, not 831. Head south past Big Sur into San Luis Obispo and you're into 805 territory instead. 831 is strictly the Monterey Bay and Salinas Valley corridor — it has never reached inland toward the Central Valley or north toward the Peninsula.

Time zone & how to dial an 831 number

California's Central Coast runs on Pacific Time (PT) — PST (UTC−8) in winter, PDT (UTC−7) during Daylight Saving Time. Dial 1, then the area code, then the seven-digit number for every call, whether local or long-distance. Wikipedia's entry on area code 831 notes that, given the region's relatively modest size in both area and population, exhaustion of the code is considered unlikely for the foreseeable future.

Key takeaways

• 831 covers Monterey, San Benito, and Santa Cruz counties on California's Central Coast.
• It split from 408 on July 11, 1998 and has never needed an overlay of its own.
• The economy blends Salinas Valley agriculture with Monterey Bay tourism and Silicon Valley overflow.
• 831 does not reach San Jose (408/669) or the coast south of Big Sur (805).
• Time zone: Pacific (PT).

Frequently asked questions