Who invented prog?

This would never be an easy one to answer without further indepth discussion and likewise debating as well.  A quick answer would be King Crimson. Here's why. While groups like Yes, Pink Floyd, Genesis and even Rush actually exsisted before Crimso offically formed, they weren't condsidered progressive rock then (though some of them might of displayed early signs of progressing but not so much during this early period). The term progressive rock didn't even exsist until it was applied by music reviewers regarding King Crimson's early live performances and record reviews in publications such as MNE and Melody Maker. And unlike any of the bands mentioned earlier, King Crimson was a progressive rock unit right from day one unlike their contemporaries like Pink Floyd (starting out as a psychedelic act), Jethro Tull (blues-rock) or Mooody Blues (R&B) for example.  Bands like the Beatles and the Mothers were exploring uncharted musical boundries in the mid-60's in essence progressing from what was the norm at the time (call it proto-prog if you will). And then a revamped Moody Blues would go and release an album entitled "Days Of Future Passed" which further instilled the movement toward prog. But one would just need to listen to "In The Court..." by KC to actually hear of what was to become beacuse there was definetly nothing like it at all prior to it's release. Such bands immediately took notice and the rest is prog history.   

...And on the 7th day He created PROG, and He was more than happy!!

From my limited point of view and to use volleyball as a metaphor...

It's an interesting topic, I think.  I haven't read through the thread, but I would have included Cream on the list.  And of course The Beach Boys.  I think one could also include bands such as The Byrds.

Very notable missing options: The Mothers of Invention and Soft Machine.  I'm voting other.

I did not vote. As many others here I believe it is not an invention but kind of evolution (yes, Darwin again).

Who invented prog? 

Procol Harum. No, wait, The Beach Boys. 

Gah, screw it, I bet it was Bach. 

Ah, but who was the first prog rock BAND? Hmm...probably Crimso. 

Beethoven.

AtomicCrimsonRush wrote: one image sums it all up

I'll grant you that this album was influential, very influential, in the development of prog.  I will not grant that this was the beginning, however.  This just added some really good stuff to the mix.

rushfan4 wrote: It was either Thomas Edison or Nikolai Tesla depending on your point of view.

Atually, without Tesla it very well could be that electronic music has progressed as far as it has. How could prog exist without mellotrons or hammond organs? Maybe the electric guitar might not have been as prominent as it has been if it wasn't for AC.

I would have to say that I think In the Court of the Crimson King is the first fully fledged prog album, although I'm not saying The Moody Blues weren't prog, they seem more cross-over to me. ITCOTCK seems a lot less conventional because Days of Future Passed still has the feeling of conventional songs within the overall album, but KC has parts that are completely unconventional, like the ending of Moon Child. Still, I guess The Moody Blues did come firster.

Other invented prog.

Wikipedia says:

The Nice were an English progressive rock band from the 1960s, known for their unique blend of rock, jazz and classical music. Their debut album, The Thoughts of Emerlist Davjack was released in 1967 to immediate acclaim. It is often considered the first progressive rock album.