A telephone area code in California. Originally (in 1947) covered all of Southern California, but its territory has shrunk over the years and it is now one of the smallest area codes in the North American Numbering Plan, covering only downtown Los Angeles and a few adjacent neighborhoods (USC, for example). The last split from 213 directly occurred in 1998, when area code 323 was formed. 323 completely surrounds 213.
213 is notable in rap culture for being referenced by prominent rappers in the 1980s as the area code at the time of Compton and Long Beach. Both cities were split into 310 upon its creation in 1991. In 1997, 562 was split from 310, taking Long Beach with it.
Yes, despite its popular association with the wealth and status of tony Westside neighborhoods and Beverly Hills, area code 310 does include Compton, as does its recent (2006) overlay, 424, though all of these places were originally 213.