Area codes have always been a thing in rap. (Just ask Ludacris.) But in 1991, Bay Area area code representation got a little murky. That's the year the East Bay ceded its 415 area code to the West Bay and Marin, and adopted 510 as its dialing prefix. For certain rap artists, the effect was utter chaos: an entire Oakland rap group called 415 disbanded, and whole swaths of East Bay rap songs referencing the 415 became obsolete.
These days, the 415 is a proud marker of San Francisco rap all across the city, from the Fillmore to Hunters Point. And 415 Day, the very definition of a call-into-work-sick Friday afternoon party, is a celebration of that culture.