6. King Crimson - 'In the Court of the Crimson King'
It's impossible to definitively say what the first true prog album was, but nobody disputes that King Crimson's 1969 debut LP, In the Court of the Crimson King, was a monumental step forward for the genre. It's hard to imagine how groups like Yes and Genesis would have evolved without this album as an influence. The lineup didn't last beyond this one LP, but songs like "In the Court of the Crimson King" and "21st Century Schizoid Man" remain the group's most famous works. The latter was even sampled by Kanye West on his last solo album. Both songs are sung by Greg Lake, who formed Emerson, Lake and Palmer a year after this album hit shelves. Robert Fripp has lost interest in King Crimson and the group is on hiatus, but it would a very fitting end if the original lineup would get together for one final concert. Sadly, this is extremely unlikely.