Crosby, Stills & Nash (CSN) were an American-British folk rock supergroup made up of David Crosby, Stephen Stills, and Graham Nash. They were known as Crosby, Stills, Nash & Young (CSNY) when joined by occasional fourth member Neil Young. 

So what made CSN so special, noted for their intricate vocal harmonies, often tumultuous interpersonal relationships, political activism, and lasting influence on US music and culture. 

Fittingly, Crosby, Stills & Nash were inducted into the Rock and Roll Hall of Fame and all three members were also inducted for their work in other groups (Crosby for the Byrds, Stills for Buffalo Springfield and Nash for the Hollies). Neil Young has also been inducted, but as a solo artist and as a member of Buffalo Springfield, not for his work with the group...

What does the future hold for CSN???  Lots of rumors swirling of a reunion but it depends on who you ask....
Crosby would welcome it....Stills is a bit more cynical saying WHY?...Nash said CSN is done (old hurt feelings)...but with next year marking 50 years, will an offer be made to reunite the guys???