Your first Prog album?

It's funny, was a fan of classical music into my teenage years, my father was a huge ELP and Genesis fan going back to their hayday, and I had been hearing songs by Pink Floyd, Yes, and ELP on the car radio since I was a child but it wasn't till college that I put it all together (though I still don't care for Genesis).  A buddy of mine (who was a pre-existing Tool fan, a band I hate with a passion to this day) and I both took notice of the music of Frank Zappa and from there expanded into the general prog world.  If the usually bland DVE hadn't accepted someone's phone request for "Montana" who knows if I'd have ever found out that music could be more than just background noise.  It was also a stroke of luck that We're Only in It for the Money was the first Zappa album I purchased (and I mean luck, I had no idea what to buy out of such a huge discography) because of how exceptionally weird it is.  I miss those days of discovery somewhat but I also think my time may have been better spent chasing women, in hindsight .

I think I was 3-4 year old when heard it. so, it was probably near 1977 (I was born in 1973)

Of course I wasn't aware what "prog rock" is.  My father was (and is) rock and jazz guitarist, and he has a good taste in music , so I grew listening father's music collection

other my "not so prog" but important influences was The Beatles and Deep Purple