Starting in the 1950s, Southern California experienced rapid expansion of telephone service, requiring area code 213 to be split five times by 1998.The first split became necessary in 1951, when most of the southern and eastern portion, including San Diego and most of Orange County, was assigned area code 714.On August 26, 1999, the NANPA approved a request by the California Public Utilities Commission for a two-phase split/overlay plan to provide area code relief for 909.(Similar plans were being considered to provide relief to the 310, 415, 510, 760 and 818 area codes as well; however, due to number rationing, all were postponed indefinitely and later permanently cancelled.)909 continued to serve small portions of Corona, Riverside, Moreno Valley, and the entire city of Calimesa, all of which are in Riverside County, as well as small portions of eastern Los Angeles and northern Orange Counties; area code 752 was returned to the numbering pool to be reassigned at a later date.