1st Prog album?

"Sgt. Pepper's..." is progressive, but it is not Progressive Rock ("progessive rock" is not the same thing as "Progressive Rock"). Neither was ITCOTCK the first Progressive Rock album. ThE NICE had already released three albums before ITCOTCK came out, and even if one were not to recognise "The Thoughts Of Emerlist Davjack" as Progressive Rock (I certainly think it is), surely there can be no argument about "Ars Longa Vita Brevis".

Come to that, GENESIS' "From Genesis To Revelaton" was released before ITCOTCK, and so were COLOSSEUM's "Those Who Are About To Die Salute You", VDGG's "Aerosol Grey Machine" and various other Progressive Rock albums.

ITCOTCK being the first Progressive Rock album seems to have become something of an urban myth. It's not correct.

There are prog elements and one surely prog number in the Byrds "Fifth Dimension", 1966; there are more than prog elements, there is an epic suite with mellotron in Steve Miller band "Children of the Future". The Moody Blues "The Days of Future Passed" and "In Search of the Lost Chord" were released Before ITCOTCK.

However it is true that ITCOTCK is a real breakthrough in the way it is not an album with progressive elements, nor an album that sounds progressive at times. It is progressive from the beginning to the end. In this way, it could be the first willingly produced progressive album.