...to Bruce Lancaster for identifying the vehicle: my wife and I couldn't figure out what we were looking at. Although my wife did insist it was a car of some sort.

Here's a Shorpy photo taken four stories further up and ten years further back.

Could that be the tail end of a paddy wagon sticking out from the side street by the Federal Building?

[I think those are the last two letters of U.S. MAIL. similar to the sign on this wagon. -tterrace]

Below is the same view from April of 2007.

This is looking north from Adams and Dearborn. I work around here - previous comments are accurate - the buildings on the east side of this photo are long gone. Monadnock is thankfully still here, and the Marquette, while a neat building, isn't as cool as the Monadnock (in my opinion).

I think the vehicle is a Holsman High-Wheeler. High wheeler cars were really made as rural vehicles, able to cope with high centers and ridiculous amounts of mud; the one in the picture, though, looks to have never been on the wrong end of a cow.

The cable car slot in the far track that goes around the Loop hasn't been used since 1906.

On the left-hand (west) side of Dearborn Street we can see (from left to right) slivers of the Monadnock Block (Burnham & Root, 1889-1891), the Federal Building (Henry Ives Cobb, 1905, now demolished), and the Marquette Building (Holabird & Roche, 1893-1895). The buildings shown here on the east side of Dearborn are all long gone.