For a number of years I walked through this door mornings
and out again (sometimes late) that night. I had a small
software business and my office was in this Ellicott Square
Building. At one time, when originally built, it was the
largest office building in the country. It covers an entire
city block, and back then, I believe that characteristic was rare.

More information here http://en.wikipedia.org/wiki/Ellicott_Square_Building

and more history here http://freenet.buffalo.edu/bah/a/main/295/index.html