Editing Aon Center (Chicago) (section)

==History==

===Construction===
[[File: Chicago - Buckingham Fountain (4284462009).jpg|thumb|View from [[Buckingham Fountain]] of the building while it was under-construction|left]]

The Standard Oil Building was constructed as the headquarters of the [[Amoco|Standard Oil Company of Indiana]]. Standard's previous home had been 910 S. Michigan Avenue. This building was constructed in 1911 by the Karpen Brothers Furniture Company and was purchased by Standard in 1927. When the new Standard Oil Building was completed in 1973, it was the tallest completed building in Chicago and the fourth-tallest in the world, earning it the nickname "Big Stan".<ref name="gss">{{cite web| website=Glass Steel and Stone| title=Aon Center| url=http://www.glasssteelandstone.com/BuildingDetail/625.php| access-date=September 25, 2007| archive-url=https://web.archive.org/web/20070826091210/http://www.glasssteelandstone.com/BuildingDetail/625.php| archive-date=August 26, 2007| url-status=usurped}}</ref> In 1974, the taller Sears Tower (now Willis Tower) in Chicago surpassed it as the tallest completed building in Chicago (the Sears Tower was also the tallest in the world). However, the Sears Tower had already been [[topped out]] in May 1973.<ref name="SearsTopping"/><ref name="archiseek"/> When the Aon Center opened as the fourth-tallest completed building in the world, it was only exceeded in height by the twin towers of the original [[World Trade Center (1973–2001)|World Trade Center]] and the [[Empire State Building]] in [[New York City]].<ref name="SearsTopping">{{cite web |last1=Nelson |first1=Bryce |title=Sears 'Topping Out' Puts Chicago On Top |url=https://www.newspapers.com/image/265469018/ |website=Newspapers.com |access-date=October 9, 2022 |language=en |date=May 7, 1973}}</ref> Originally clad in [[marble]], the Aon Center was also the tallest marble-clad building in the world.<ref name="archiseek">{{cite web |title=1973 – Aon Center, Chicago, Illinois |url=https://www.archiseek.com/2009/1973-aon-center-chicago-illinois/ |website=Archiseek - Irish Architecture |access-date=October 9, 2022 |date=September 20, 2009}}</ref>

The building employs a tubular steel-framed structural system with V-shaped perimeter columns to resist [[earthquakes]], reduce sway, minimize column bending, and maximize column-free space.  This construction method was also used for the original World Trade Center twin towers in [[New York City]].

===Refacing===
[[File:Aon Center during resurfacing with temporary work elevators in its corners (22427576248) (1).jpg|thumb|Aon Center in the 1990s during its refacing, with temporary work [[elevators]] erected in the building's corners|left]]

When completed, it was the world's tallest [[marble]]-clad building, sheathed entirely with 43,000 slabs of Italian [[Carrara marble]].  The marble used was thinner than previously attempted in cladding a building, which soon proved to be a mistake.  On December 25, 1973, during construction a 350-pound marble slab detached from the façade and penetrated the roof of the nearby [[One Prudential Plaza|Prudential Center]].<ref>Chicago Tribune, December 26, 1973</ref>  In 1985, inspection found numerous cracks and bowing in the marble cladding of the building.  To alleviate the problem, stainless steel straps were added to hold the marble in place.<ref name="gss" />  Later, from 1990 to 1992, the entire building was refaced with [[Mount Airy, North Carolina|Mount Airy]] white [[granite]] at an estimated cost of over $80 million.<ref name="emporis" /><ref name="globe">{{cite news |last=McMillan |first=Greg |publication-date=June 12, 2007 |title=Two buildings, two cities, one problem |periodical=[[The Globe and Mail]] |publication-place=Toronto |url=https://www.theglobeandmail.com/report-on-business/two-buildings-two-cities-one-problem/article17996906/ |access-date=September 25, 2007}}</ref> Amoco was reluctant to divulge the actual amount, but it was well over half the original price of the building, without adjustment for inflation. Two-thirds of the discarded marble was crushed and used as landscaping decoration at Amoco's refinery in [[Whiting, Indiana]], one-sixth was donated to [[Governors State University]], in [[University Park, Illinois|University Park]], and one-sixth donated to Regalo, a division of Lashcon Inc.  Under a grant from the Illinois Department of Rehabilitative Services, Regalo's 25 handicapped workers carved the discarded marble into a variety of specialty items such as corporate gifts and mementos including desk clocks and pen holders.<ref name="emporis" /><ref name="UIC OSWM">{{cite web |url=http://www.p2pays.org/ref/24/23685.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.p2pays.org/ref/24/23685.pdf |archive-date=October 9, 2022 |url-status=live |title=Construction and Demolition Waste: Generation, Regulation, Practices, Processing, and Policies |first1=Stephen D. |last1=Cosper |author2=William H. Hallenbeck |author3=Gary R. Brenniman |date=January 1993 |publisher=University of Illinois at Chicago, Office of Solid Waste Management |access-date=March 26, 2010 | page=31}}</ref> The building's facade somewhat resembles that of the North and South tower of the former [[World Trade Center (1973-2001)|World Trade Center]] Complex due to the upward flow of the columns.

===Designation===
The Standard Oil Building was renamed the Amoco Building when the company changed names in 1985.  In 1998, Amoco sold the building to [[The Blackstone Group]] for an undisclosed amount, estimated to be between $430 and $440 million.<ref name="emporis" /><ref name="gss" /> It was renamed as the Aon Center on December 30, 1999, although the [[Aon Corporation]] would not become the building's primary tenant until September 2001.<ref>{{cite web| title=AON Center Chicago: Skyscraper Architecture| url=https://www.e-architect.co.uk/chicago/aon-center| first=David| last=McManus| date=July 12, 2018| website=e-Architect| access-date=January 20, 2020}}</ref>  In May 2003, Wells Real Estate Investment Trust, Inc. acquired the building for between $465 and $475 million.<ref name="emporis" /><ref>{{cite web |website=Miller Cicero, LLC |title=Trophy Building Sale Sets New Record |date=October 7, 2003 |url=http://www.millercicero.com/press/files-view.php?ViewNode=1066154585cVxrI |access-date=September 25, 2007 |archive-url=https://web.archive.org/web/20070518025208/http://www.millercicero.com/press/files-view.php?ViewNode=1066154585cVxrI  |archive-date=May 18, 2007 |url-status=dead}}</ref> On August 10, 2007, Wells Real Estate Investment Trust, Inc. changed its name to Piedmont Office Realty Trust, Inc.)<ref>{{cite web |website=Piedmont Office Realty Trust, Inc. |title=Wells REIT Changes Name to Piedmont Office Realty Trust |url=http://www.piedmontreit.com/cms/content/view/139/63 |access-date=August 10, 2007 |url-status=dead |archive-url=https://web.archive.org/web/20080610020230/http://www.piedmontreit.com/cms/content/view/139/63 |archive-date=June 10, 2008}}</ref>

Real estate investors Mark Karasick and Victor Gerstein acquired the building from Piedmont in 2015 for $713 million.<ref name="Owners"/>

===Planned observation deck===
{{update section|date=April 2024}}
On May 14, 2018, the building's owners unveiled a $185 million proposal for an observatory featuring a thrill ride on the roof called the Sky Summit, the world's tallest exterior elevator, and new entrance pavilion. The observatory was supposed to be completed in 2022, but the [[COVID-19 pandemic]] had been announced to have delayed construction plans by about a year.<ref>{{cite news| title=Aon Center's planned observation deck, Chicago's third, could create competition for tourist dollars| url=http://www.chicagotribune.com/business/ct-biz-chicago-observation-decks-20180511-story.html| first1=Ally| last1=Marotti| first2=Blair| last2=Kamin| date=May 15, 2018| newspaper=Chicago Tribune| access-date=January 20, 2020}}</ref><ref>{{Cite web|title=Construction halted for Aon Center observatory in Chicago due to coronavirus pandemic|url=https://www.usatoday.com/story/travel/news/2020/06/29/coronavirus-construction-halted-aon-center-observatory-chicago/3277266001/|access-date=November 28, 2020|website=USA TODAY|language=en-US}}</ref>