Best progressive rock album side

My intent is to seek albums which I may not own from the recommendations of you all. I ranked best sides of progressive rock albums on vinyl that I own and came up with the following list. I don't want it to undermine anything else that an artist has created. I love it all but as far as start to finish on one side this is what I came up with.

#1: Supper's Ready

#2: Terrapin Station

#3: Atom Heart Mother

#4 The Court of the King Crimson

#5 Echoes

Of course there are many more. Some may not be complete sides like Atom Heart Mother but the intent of the artisan was to make it a complete side. I had a very hard time deciding between #1 and #2. Both are very worthy in my mind.