I profess no knowledge re. Professor Longhair...

I'll second Onhwy61: Queen Mary is one of my all time favorite recordings.
FWIW Prof spawned a generation (or two) of blues piano players in N'awlins. You may want to check out James Boooker's "Lost Paramount Tapes" which is my favorite record from any of Prof's "disciples".

Check out the Aligator Records compliations as well.

Disregard everything listed above. It makes no sense to get into latter 'Fess" first.

There are three early material compilation albums that one should seek out:

"Professor Longhair New Orleans Piano" on Atlanic label.

"1949 Professor Longhair" on the Classics (French) label.

"Mardi Gras in New Orleans" on the Proper (British) label

Me, I'd go with the Proper disc. Twenty-three tracks with good notes and photos for under ten bucks!

Theduke makes a point, if you are going to build a collection, why not start at the beginning?

HOWEVER, if you're coming from a rock'n'roll listener's context and just starting out with blues piano , the later recordings are much more accessible - in particular Queen Mary - and a better place to start. One of the joys of migrating from rock music to piano blues is recognizing rock's roots in a different genre. About 15 years ago, I found Prof very rewarding for this reason and now listen to piano blues as much as, if not more than, rock music.

BTW New Orleans Piano and Madi Gras in NO are, as theduke notes, great records (I've managed to miss 1949 but will seek it out now).

Others not yet mentioned would include House Party in NO and Ball The Wall.

Martykl makes a good point. I think it is an eay transition into blues from rock. Working backward is a learning experiance. Work your way back to wax cylinder recordings from the Library of Congress and you can fully appreciate what is currently available (and justifiably criticize much of it for having bastardized all things good about music).

Have fun!