The Chicago skyscraper that shed its marble skin to survive a structural crisis

Countries & Cities · Published 3 October 2026 Swipe more like this →

In short: Completed in 1973 as the Standard Oil Building, this Chicago icon was once the world's tallest marble-clad structure. But the thin Italian stone proved dangerous, leading to a massive, multi-million dollar replacement project. Today, the building stands as a testament to both architectural ambition and the hazards of experimental design.

Designed by Edward Durell Stone and Perkins and Will, the Aon Center—originally known as the Standard Oil Building—reached 1,136 feet upon its 1973 completion. At the time, it was the fourth-tallest building globally and the tallest in Chicago, earning the nickname Big Stan. Its structural integrity relied on a tubular steel-framed system with V-shaped perimeter columns, a design choice shared with the original World Trade Center twin towers to maximize interior space and minimize sway.

The building’s initial aesthetic was defined by 43,000 slabs of Italian Carrara marble. However, the decision to use thinner stone than previously attempted became a liability. In December 1973, a 350-pound slab fell, piercing the roof of the nearby Prudential Center. By 1985, inspections revealed widespread bowing and cracking. The solution was drastic: between 1990 and 1992, the entire façade was replaced with Mount Airy white granite. This renovation cost over $80 million, a figure exceeding half the building's original construction price.

The discarded marble found a second life, with two-thirds crushed for landscaping at an Indiana refinery and the remainder donated to Governors State University and a division of Lashcon Inc. known as Regalo. At Regalo, workers carved the stone into corporate gifts. Since its marble-clad days, the building has undergone several ownership changes, including acquisitions by The Blackstone Group and Piedmont Office Realty Trust. In 2018, owners proposed a $185 million observatory project called Sky Summit, though the COVID-19 pandemic delayed these plans.

Today, the Aon Center remains a prominent feature of the Chicago Loop, housing major firms like Aon, Kraft Heinz, and the Blue Cross Blue Shield Association. While it no longer holds the title of Chicago's tallest—having been surpassed by the Willis Tower in 1974—its history serves as a cautionary tale regarding the intersection of architectural innovation and material science.

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