When did undergound music first become its own subculture of hip hop?

I believe all Hip-Hop started as "undergound" untill the late 80's and through the 90's when the "mainstream" took over and made it all about Entertainment. They took over the creative controll to market this music better... There were plenty of kats who stayed back...so i would say in the mid 90's things took off.... I would much rather call it Independent music rather than 'Underground"