When you've been in the game as long as the hip-hop greats, you become somewhat of a curmudgeon. Public Enemy's Chuck D and Rakim could be considered two examples. However, when you've contributed to the culture as much as those two have, you kind of have the right to. KRS-One, who's particularly reclusive, is another example. The South Bronx-born rhymer reaches the golden age of 51 today (Aug. 20).

KRS-One was one of the ruggedest rhymers of the '80s, combining Caribbean patois with concrete toughness. He was a true force when he was part of Boogie Down Productions; Criminal Minded is considered a hallmark in East Coast hip-hop. KRS-One dissed Marley Marl's crew and the entirety of Queens with the famous "The Bridge Is Over" and later infamously tossed softcore hip-hop group P.M. Dawn off of the stage during a concert in response to comments made during an interview. KRS-One was not to be messed with.

However, the rapper's music started to take a shift after Boogie Down Productions co-member Scott La Rock was shot to death after Criminal Minded. The follow-up, By All Means Necessary, moved toward socially conscious songs that spoke on violence and police corruption.  KRS-One also became known as The Teacher and founded the Stop the Violence Movement, a response to violence in African-American communities.

He scored another cult classic with his solo debut, Return of the Boom Bap, in 1993. But the MC soon slipped out of the spotlight. Part of that was his own doing; he rallied against the changing direction of hip-hop and threatened to sue radio stations for playing his songs. KRS-One may not want much to do with hip-hop as it is now, but at the root of the culture, he's still an essential piece of its history.

Watch KRS-One/Boogie Down Production's "My Philosophy" Video

Watch KRS-One's "Sound of da Police" Video

More From B93