A competition was held for the design of the new building, but the fee demanded by first prize winner George I. Barnett was deemed too costly, so the project was awarded to second-place Lee and Annan, at the time a relatively new architectural firm.

Work began in 1873 and was completed in December 1875 at a total construction cost of $2 million. It was the largest building on the riverfront, designed in a Venetian version of the Italianate style. While it appeared to be one mammoth structure, it was actually two buildings connected by a light court.

An iron truss system that supported the roof allowed the second and third stories of the western half to be a single space, 235 feet long and 98 feet wide and 65 feet tall. At the time, this was the largest open interior space in the country. The room could hold 10,000 people, and hosted the 1876 Democratic National Convention [Barkley 37-39, Lowic 109-111].