This is one of those things that I thought was really cool as a kid, then forgot about completely and now can't find any information on it. We always called it the air raid siren those many years ago. It's located on a residential street way at the top of Monrovia. Must have been really annoying to those living nearby.
Maybe they could get it working again and use it as a fire warning siren. When it goes off, evacuate!
dave over at 1916home.net
and now... (drumroll please)...