It’s one of the Indestructibles: a structure big enough and nice enough so it’s always off the table for demolition. In a bigger city, perhaps it would have gone down to some big slab, but not here.
It was built in two phases. Can you tell? the corner structure was built in 1924, and as the decade become more prosperous and the incidence of human suffering did not abate, another wing was built to house doctors, specialists, dentists, and other ministers to human frailty. The postcard actually shows the two phases with different styles; the original section seems based on a photograph, and the rest is drawn in.
As for which photo it might be based upon . . .