Area code 840 is located in California, USA, and is an overlay numbering plan area (NPA) for the far-eastern part of Los Angeles County and southwestern San Bernardino County. It was added to the numbering plan area to form an overlay complex effective February 23, 2021, and is part of the 909/840 area code overlay. The 909 area code was created on November 14, 1992, in an area code split of 714. The 840 area code was picked because it doesn’t conflict with any adjacent area codes, and there are no dialing conflicts that will arise when the new area code is implemented.

Some of the main locations covered by area code 840 include San Bernardino, Rancho Cucamonga, Pomona, Chino, Fontana, Claremont, Diamond Bar, Colton, Rialto, and Upland. Individuals and businesses that currently have 909 telephone numbers do not need to change them, and customers requesting new or additional telephone numbers will be assigned either a 909 or 840 area code depending on availability.

To call a number with area code 840, you need to dial “1” plus the area code plus the telephone number for the call to go through, even if you live in the same area code. The new dialing protocol is part of a system to allow a continuous supply of new phone numbers for the southwestern portion of San Bernardino County, the eastern part of L.A. County, and slivers of Orange and Riverside Counties currently served by an area code that’s synonymous with the Inland Empire.