Sgt. Pepper's Lonely Hearts Club Band

The Beatles are not progressive in the true sense but, this record is more than rock: it contains the early psychedelic patterns and it also contains basic progressive elements that surely contributed to make the progressive rock style itself to emerge. This album is often considered the starting point of progressive rock. Read more here. 

Syd Barrett

Syd Barrett was an English singer, songwriter, guitarist, and painter, best remembered as a founder member of the band Pink Floyd. He was the lead vocalist, guitarist, and primary songwriter during the band's psychedelic years, providing major musical and stylistic direction in their early work. He is also credited with creating their name, but left the group in April 1968. In 1969, Barrett started off a brief solo career. Read more here.