Aon Center Chicago

The Aon Center, situated in the Chicago metropolitan area, stands as a modern marvel of skyscraper design. This impressive structure, located at 200 E. Randolph St., Chicago, Illinois 60601, was brought to life through the collaborative efforts of architects Edward Durell Stone and The Perkins and Will partnership. Construction commenced in 1970, and by 1973, it had become a defining presence in the Chicago skyline.

With its 83 above-ground floors and a towering height of 1,136 feet (346 m), the Aon Center proudly claims the title of the fourth-tallest building in Chicago. Notably, it is surpassed in height only by the Willis Tower, Trump International Hotel and Tower, and St Regis Chicago within the city.

Currently owned by Mark Karasick and Victor Gerstein, this architectural gem is an exemplary office building, reflecting a modern architectural style. It houses prominent organizations, including Aon and one of Kraft Heinz's headquarters. In the past, it served as the world headquarters of Amoco before its merger into BP.

Construction and History:

The Aon Center's roots trace back to its predecessor, the Standard Oil Building, which was erected as the headquarters of the Standard Oil Company of Indiana. Prior to this, Standard Oil had occupied 910 S. Michigan Avenue, a building acquired in 1927. The new Standard Oil Building, completed in 1973, boasted the title of Chicago's tallest completed building at the time. Its monumental presence earned it the affectionate nickname "Big Stan." However, in 1974, the Sears Tower (now Willis Tower) surpassed it as Chicago's tallest building, although the latter had already reached its full height in May 1973. When the Aon Center emerged as the world's fourth-tallest completed building, it was only surpassed globally by the twin towers of the original World Trade Center and the Empire State Building in New York City.

The Aon Center's innovative structural system, featuring tubular steel framing and V-shaped perimeter columns, enhances its earthquake resistance, minimizes sway, reduces column bending, and maximizes unobstructed interior space. This construction method was notably employed in the original World Trade Center twin towers in New York City.

An interesting historical feature is the building's initial cladding with 43,000 slabs of Italian Carrara marble, marking it as the world's tallest marble-clad building upon completion. However, the thinner marble slabs proved problematic. On December 25, 1973, during construction, a 350-pound marble slab detached from the façade and punctured the roof of the nearby Prudential Center. In 1985, inspection revealed cracks and bowing in the marble cladding, necessitating the addition of stainless steel straps for reinforcement. Subsequently, from 1990 to 1992, the entire building underwent a transformation, refaced with Mount Airy white granite, at a cost exceeding $80 million. Notably, over two-thirds of the removed marble was repurposed for landscaping at Amoco's refinery in Whiting, Indiana, with a portion donated to Governors State University and Regalo, a division of Lashcon Inc., which employed handicapped workers to craft various items from the discarded marble.

The Aon Center's façade exhibits a resemblance to the North and South towers of the former World Trade Center Complex, reflecting the upward flow of its columns.

Renaming and Ownership:

Originally known as the Standard Oil Building, it was rebranded as the Amoco Building in 1985 following the company's name change. In 1998, Amoco sold the building to The Blackstone Group for an undisclosed sum, estimated between $430 and $440 million. Then, on December 30, 1999, it adopted the name Aon Center, though Aon Corporation became its primary tenant in September 2001. In May 2003, Wells Real Estate Investment Trust, Inc. acquired the building for approximately $465 to $475 million. Notably, on August 10, 2007, Wells Real Estate Investment Trust, Inc. underwent a name change, becoming Piedmont Office Realty Trust, Inc.

Current Ownership:

In 2015, real estate investors Mark Karasick and Victor Gerstein acquired the Aon Center from Piedmont for a substantial $713 million.

Planned Observation Deck:

Looking to the future, the Aon Center's owners revealed an exciting vision in May 2018—a $185 million proposal for an observatory. This observatory was set to feature a thrilling rooftop attraction known as the Sky Summit, touted as the world's tallest exterior elevator, and a new entrance pavilion. Initially planned for completion in 2022, the construction schedule faced delays of approximately a year due to the COVID-19 pandemic.