Monadnock Building

The Monadnock Building is a skyscraper located at 53 West Jackson Boulevard in the south Loop community area of Chicago, Illinois.

The north half of the building was designed by the firm of Burnham & Root and built starting in 1891.

The tallest commercial iron frame building with a load-bearing masonry exterior wall ever constructed, it employed the first portal system of wind bracing in America. Its decorative staircases represent the first structural use of aluminum in building construction.

The south half, constructed in 1893, was designed by Holabird & Roche and is similar in color and profile to the original, but the design is more traditionally ornate.

When completed, it was the largest office building in the world.

The building was remodeled in 1938 in one of the first major skyscraper renovations ever undertaken—a bid, in part, to revolutionize how building maintenance was done and halt the demolition of Chicago's aging skyscrapers.