Charter Oak is a census-designated place (CDP) in Los Angeles County, California, approximately east of downtown Los Angeles. The population was 9,310 at the 2010 census, up from 9,027 at the 2000 census.
Charter Oak is located in the eastern San Gabriel Valley, situated along Arrow Highway in between Covina to the south, Glendora to the north and San Dimas to the east. Some residents refer to the CDP portion as the "unincorporated part of Covina".
Originally a small agricultural town (primarily citrus orchards) centered on the intersection of Arrow Highway and Bonnie Cove Avenue, population growth greatly expanded the area recognized as "Charter Oak". Since the 1960s, it has been known as a "bedroom community" suburb of Los Angeles and commercial agriculture is nearly gone.
Today, the generally accepted boundaries of Charter Oak are I-210 to the north, Valley Center Avenue to the east, Covina Hills Road to the south and Grand Avenue to the west. In the mid-1960s, Glendora annexed the area north of Arrow Highway and Covina annexed much of the area south of Arrow Highway. Several small "county islands" of unincorporated area remained within the annexed portions of Covina and Glendora until the 1980s. The remainder forms the CDP.