[ardecila]

I doubt it. All things equal, it would be a massive amount of square footage close to the economic powerhouse of the city: Michigan Avenue. It would probably have retained a mix of uses, changing dynamically to reflect the city's evolving economy, but it would still be well-used today.

The Post Office has had so many non-starts largely because of its location, not its size. It is in the wrong place for most of the serious proposals that have come its way... nobody really wants to live, or stay, in that area yet.

The Merchandise Mart, obviously, has found a successful model by combining showrooms and retail with exhibition space and offices.

denizen: I believe the Morrison bit the dust because First Chicago wanted an entire block, and Morrison happened to own one. On any other block, there would have been multiple owners, and some of them probably would have refused to sell. Morrison, faced with a declining downtown and fewer and fewer guests, folded up shop and sold out.