Demolished in 1912, the Chicago Opera House was Cobb's first skyscraper. Ten stories in height and L-shaped in plan, the building was probably of mixed masonry and iron construction. The dimensions of the lot upon which the building stood were 107 feet on Washington St. by 180 feet on Clark St. The street facades were composed of plate glass windows, divided only by slender, metal mullions. Alternating narrow and wide brick piers rise from a cornice above the second story. The façade is very open with paired rectangular windows, broken only by a row of arched openings on the eighth story and ending in a complex cornice. The theatre occupied the first five stories of the interior of the L. Though no pictures of the theater interior have been located, according to an April 1885 Inland Architectarticle, the theater was located in the court and joined on two sides only. With its anticipation of the curtain wall and lack of ornament, the Chicago Opera House exhibited the aesthetic possibilities of curtain framing, but has generally been overshadowed by William LeBaron Jenney's contemporaneous Home Insurance Building.
Now a community museum, the three-story, Richardsonian Romanesque J.B. Watkins Building occupies a corner lot and is constructed of red brick trimmed with a lighter rock-faced material. The narrower front of the building has an arched entrance set to the side, a group of four arched windows above a carved sill, and a steep gable with one arched window at the attic level. The longer side of the building has three steep gabled dormers with large openings to the third floor and lancets at the attic level.
The demolished Owings Building was a reversion to picturesque eclecticism, and as such, was deemed old-fashioned soon after it was built. The building used exterior masonry construction combined with iron interior supports. A contemporary description in Industrial Chicago highlights elements used from various architectural styles: a Norman-Gothic entrance, pilasters running from the fourth to eighth stories, a cornice and frieze at the eighth story, a corner bay ending in a finial-topped spire, and numerous gables. The interior featured tile-covered partitions and floors. Though the building's eclecticism was unpopular at the time it was built, its aesthetic foreshadowed Cobb's Liberty Tower of 1909 (see above) and even Raymond Hood and John Howell's 1922 Tribune Tower design.