The 1919 addition. Less than two decades after the Chamber of Commerce was constructed, an annex was built. Stylistically, it's a regression - from Sullivan's ideas we've gone right back to the classical vocabulary.

On the other hand, it's a handsome building. The lower building - tinted red for the postcard - would survive for another seven decades; unless I'm mistaken, that would be the home of the Little Red Wagon, a famous Star-Tribune journalist watering hole. (And by "water" I mean "liquor.") This card may explain the origin of the name - from Cadillac to Wagon, perhaps. Or maybe "wagon," as in "you're falling off it."