Area codes 909 and 840

Area codes 840 and 909 are California telephone area codes that cover far eastern Los Angeles County and southwestern San Bernardino County. The 909 area code was split from area code 714 on November 14, 1992. By August 1993 use of the new area code became mandatory. Western Riverside County was split off from 909 into area code 951 on July 17, 2004. 909 still covers small portions of Corona, Riverside, and Moreno Valley, which are in Riverside County.

Map of California numbering plan areas (blue) and border states. Area codes 840 and 909 are shown in red.

Originally on the same date that 951 split off from 909, the area retaining the 909 area code was to be overlaid by a new area code 752. However, as a result of number pooling, this overlay plan was shelved prior to the 909/951 split and 752 was returned to the NANPA numbering pool to be assigned at a later date. On July 23, 2019, the California Public Utilities Commission announced that the 909 area code will be overlaid with area code 840 on February 23, 2021. Permissive calling will start come July 2020.[1]

840 is California's 36th area code. When it goes into effect, exactly half of California's 24 geographically designated area code zones will be overlay areas while the other 12 will retain single-area code status.

Under the traditional NANPA plan, 909 was the "worst" all-purpose area code for pulse dialers (due to the excessive time required for each spin of the dial to return before the next digit could be dialed; the only "worse" area code for pulse dialing is the pay-for-service area code 900), in contrast to area codes such as 212 and 213, although it was implemented long after most people stopped using rotary phones. Area code 909 also has the distinction of being the second to last new area code with a 0 as the middle digit to go online. (The rest of the original style area codes afterwards were 905 [which was previously a "dialaround" code for Mexico] and the last of the N10 area codes that were allowed before the format changed in 1995.)