Once you know that's the hotel Windsor in the middle, the rest is easy! The Windsor went up in 1927, and was leased to Conrad Hilton - it was the first hotel to bear his name. (I'm paraphrasing what every single page on the internet says about it, which is the exact same thing in the exact same words.) The Windsor name was applied when Connie's lease was up in '45.
It's a retirement home now.