What does the number 18 on a Raiders jersey have to do with gangs?

Question

I go to a public high school in the Bay Area, and this year, we are not allowed to wear Randy Moss jerseys from when he played on the Oakland Raiders. I personally wouldn't wear the jersey, but no one had any idea what it meant. Does anyone know?

Answer 1

18th st

Answer 2

18th Street

Los Angeles gang