The area code 925 is located in Antioch, California.
Area code 925 serves the inland East Bay, including Antioch, California, in northeastern Contra Costa County. Centered along the San Joaquin River at the edge of the Sacramento–San Joaquin Delta, Antioch sits in a fast-growing corridor linked by State Route 4. The 925 area code was created in a split from 510 to better serve this expanding region and its communities. According to the North American Numbering Plan Administration, area code 925 was established on March 14, 1998.
Major cities and communities covered by 925 include:
This area code reaches notable East Bay landmarks such as Mount Diablo State Park, the John Muir National Historic Site in Martinez, and the Concord Pavilion. It also includes the Lawrence Livermore National Laboratory in Livermore and the Antioch Bridge over the San Joaquin River. The region observes Pacific Time (PT) and follows daylight saving time, which is helpful for scheduling calls with 925 phone numbers. “Mount Diablo rises to 3,849 feet,” a prominent peak visible across the Bay Area (California State Parks).
Whether you’re dialing a local Antioch business or reaching friends across the East Bay, 925 connects much of central and eastern Contra Costa County and the Tri‑Valley. Its mix of suburban centers, historic downtowns, and major parks reflects the character of the inland East Bay. With Antioch as a key hub on the Delta, 925 ties together everyday life, commerce, and outdoor adventure across this part of Northern California.