Chicago Stock Exchange, view from northeast. (Contemporary post card, collection of the author)
The Stock Exchange, a project to fund a new trading room through the provision of office space for traders and associated businesses, alternated bay windows with flat, tripartite windows, in a hybrid elevation that emphasized verticality– a theme that Sullivan would soon propose as the skyscraper’s most basic expression.
Taken from Chicago Skyscrapers, 1871-1934 (University of Illinois Press, June 2013).