Episode Details

In 1884 Chicago officials halted construction of the Home Insurance Building at LaSalle and Adams because it weighed only about a third of what a normal building its size should, and they feared it would collapse or blow over. Architect William LeBaron Jenney, an engineer at heart, had replaced thick load-bearing masonry with an iron and steel skeleton. He showed an investigating committee that rigid moment connections turned the frame into one brace that spread wind loads through the whole structure, and the halt was lifted. Completed in 1885 at 10 stories and 138 feet, it hung its brick facade on steel shelf angles floor by floor, so no wall carried the weight of the walls above it.

Jenney also wrapped the iron in concrete and hollow terracotta to protect it from fire, a pressing concern after the Great Chicago Fire of 1871, and the frame was sound enough that two more floors were added in 1891. The title of first skyscraper is contested: the Ditherington Flax Mill had an iron frame in 1797, Philadelphia's Broad Street Station used a steel frame with a curtain wall in 1881, and Leroy Buffington patented a skeleton system in 1888. Jenney's claim rests on putting height, full framing, and fireproofing together. The building lasted only 46 years. With 90 percent occupancy against 96 percent nearby, it was demolished in 1931 for the Field Building.

• Why load-bearing masonry works like a pyramid and runs out of usable floor space as it rises
• The shelf angle system that lets each floor carry only its own row of bricks, like books on separate shelves
• Other contenders: Badger's grain elevators, Peter B. Wright's 1874 columns, the Equitable Life and Montauk buildings
• How the idea of highest and best use doomed a building that was still 90 percent leased in 1929
• The bronze plaque placed in the Field Building lobby in 1932 calling Jenney's building the father of the skyscraper