The 1905 Long Beach Municipal Auditorium was a wood frame building seating 6000 that was built on the beach near The Pike amusement area.
It was eventually replaced in 1932 by a gargantuan art deco edifice that should have lasted for the ages but was demolished for the 1978 Terrace Theatre and other structures of the Long Beach Convention Center.
What you're seeing here is a view from the Los Angeles Public Library of the Symphony Hall space of the 1932 building. Click on the image to go to the full size view on the Library's website.
At long last, I got a page up on the two Long Beach Municipal Auditoria (or three, if you count the Terrace Theatre). Check it out and let me know what you think.