72
Global
Height rank

Aon Center

Chicago

This project will be renovated and replaced by Aon Center (Renovation)

Height
1
To Tip:

Height is measured from the level of the lowest, significant, open-air, pedestrian entrance to the highest point of the building, irrespective of material or function of the highest element (i.e., including antennae, flagpoles, signage and other functional-technical equipment).

362.5 m / 1,189 ft
2
Architectural:

Height is measured from the level of the lowest, significant, open-air, pedestrian entrance to the architectural top of the building, including spires, but not including antennae, signage, flag poles or other functional-technical equipment. This measurement is the most widely utilized and is employed to define the Council on Tall Buildings and Urban Habitat (CTBUH) rankings of the "World's Tallest Buildings."

346.3 m / 1,136 ft
3
Occupied:

Height is measured from the level of the lowest, significant, open-air, pedestrian entrance to the highest occupied floor within the building.

328 m / 1,076 ft
1 2 3 Aon Center Outline
Floors
Above Ground

The number of floors above ground should include the ground floor level and be the number of main floors above ground, including any significant mezzanine floors and major mechanical plant floors. Mechanical mezzanines should not be included if they have a significantly smaller floor area than the major floors below. Similarly, mechanical penthouses or plant rooms protruding above the general roof area should not be counted. Note: CTBUH floor counts may differ from published accounts, as it is common in some regions of the world for certain floor levels not to be included (e.g., the level 4, 14, 24, etc. in Hong Kong).

83
Below Ground

The number of floors below ground should include all major floors located below the ground floor level.

5
Height 346.3 m / 1,136 ft
Floors 83
Official Name
The current legal building name.

Aon Center

Other Names
Other names the building has commonly been known as, including former names, common informal names, local names, etc.

Amoco Building, Standard Oil Building

Type
CTBUH collects data on two major types of tall structures: 'Buildings' and 'Telecommunications / Observation Towers.' A 'Building' is a structure where at least 50% of the height is occupied by usable floor area. A 'Telecommunications / Observation Tower' is a structure where less than 50% of the structure's height is occupied by usable floor area. Only 'Buildings' are eligible for the CTBUH 'Tallest Buildings' lists.

Building

Status
Completed
Architecturally Topped Out
Structurally Topped Out
Under Construction
Proposed
On Hold
Never Completed
Vision
Competition Entry
Canceled
Proposed Renovation
Under Renovation
Renovated
Under Demolition
Demolished

Completed

Completion

1973

Country
The CTBUH follows the United Nations's definition of Country, and thus uses the lists and codes established by that organization.

United States

City
The CTBUH follows the United Nations's definition of City, and thus uses the lists and codes established by that organization.

Chicago

Function
A single-function tall building is defined as one where 85% or more of its usable floor area is dedicated to a single usage. Thus a building with 90% office floor area would be said to be an "office" building, irrespective of other minor functions it may also contain.

A mixed-use tall building contains two or more functions (or uses), where each of the functions occupy a significant proportion of the tower's total space. Support areas such as car parks and mechanical plant space do not constitute mixed-use functions. Functions are denoted on CTBUH "Tallest Building" lists in descending order, e.g., "hotel/office" indicates hotel function above office function.

office

Structural Material
Steel
Both the main vertical/lateral structural elements and the floor spanning systems are constructed from steel. Note that a building of steel construction with a floor system of concrete planks or concrete slab on top of steel beams is still considered a “steel” structure as the concrete elements are not acting as the primary structure.

Reinforced Concrete
Both the main vertical/lateral structural elements and the floor spanning systems are constructed from concrete which has been cast in place and utilizes steel reinforcement bars.

Precast Concrete
Both the main vertical/lateral structural elements and the floor spanning system are constructed from steel reinforced concrete which has been precast as individual components and assembled together on-site.

Mixed-Structure
Utilizes distinct systems (e.g. steel, concrete, timber), one on top of the other. For example, a steel/concrete indicates a steel structural system located on top of a concrete structural system, with the opposite true of concrete/steel.

Composite
A combination of materials (e.g. steel, concrete, timber) are used together in the main structural elements. Examples include buildings which utilize: steel columns with a floor system of reinforced concrete beams; a steel frame system with a concrete core; concrete-encased steel columns; concrete-filled steel tubes; etc. Where known, the CTBUH database breaks out the materials used in a composite building’s core, columns, and floor spanning separately.

steel

Official Website

Aon Center

Height
Architectural
Height is measured from the level of the lowest, significant, open-air, pedestrian entrance to the architectural top of the building, including spires, but not including antennae, signage, flag poles or other functional-technical equipment. This measurement is the most widely utilized and is employed to define the Council on Tall Buildings and Urban Habitat (CTBUH) rankings of the "World's Tallest Buildings."

346.3 m / 1,136 ft

To Tip
Height is measured from the level of the lowest, significant, open-air, pedestrian entrance to the highest point of the building, irrespective of material or function of the highest element (i.e., including antennae, flagpoles, signage and other functional-technical equipment).
362.5 m / 1,189 ft
Occupied
Height is measured from the level of the lowest, significant, open-air, pedestrian entrance to the highest occupied floor within the building.
328.0 m / 1,076 ft
Floors Above Ground
The number of floors above ground should include the ground floor level and be the number of main floors above ground, including any significant mezzanine floors and major mechanical plant floors. Mechanical mezzanines should not be included if they have a significantly smaller floor area than the major floors below. Similarly, mechanical penthouses or plant rooms protruding above the general roof area should not be counted. Note: CTBUH floor counts may differ from published accounts, as it is common in some regions of the world for certain floor levels not to be included (e.g., the level 4, 14, 24, etc. in Hong Kong).

83

Floors Below Ground
The number of floors below ground should include all major floors located below the ground floor level.

5

# of Parking Spaces
Number of Parking Spaces refers to the total number of car parking spaces contained within a particular building.

679

Tower GFA
Tower GFA refers to the total gross floor area within the tower footprint, not including adjoining podiums, connected buildings or other towers within the development.

334,448 m² / 3,599,968 ft²

Rankings
#
72
Tallest in the World
#
11
Tallest in North America
#
11
Tallest in United States
#
4
Tallest in Chicago
#
27
Tallest Office Building in the World
#
7
Tallest Office Building in North America
#
7
Tallest Office Building in United States
#
2
Tallest Office Building in Chicago
#
5
Tallest Steel Building in the World
#
4
Tallest Steel Building in North America
#
4
Tallest Steel Building in United States
#
2
Tallest Steel Building in Chicago
Construction Schedule
1970

Construction Start

1973

Completed

1992

Recladding

Architect
Design

Usually involved in the front end design, with a "typical" condition being that of a leadership role through either Schematic Design or Design Development, and then a monitoring role through the CD and CA phases.

Structural Engineer
Design

The Design Engineer is usually involved in the front end design, typically taking the leadership role in the Schematic Design and Design Development, and then a monitoring role through the CD and CA phases.

MEP Engineer
Design

The Design Engineer is usually involved in the front end design, typically taking the leadership role in the Schematic Design and Design Development, and then a monitoring role through the CD and CA phases.

Contractor
Main Contractor

The main contractor is the supervisory contractor of all construction work on a project, management of sub-contractors and vendors, etc. May be referred to as "Construction Manager," however, for consistency CTBUH uses the term "Main Contractor" exclusively.

Other Consultant

Other Consultant refers to other organizations which provided significant consultation services for a building project (e.g. wind consultants, environmental consultants, fire and life safety consultants, etc).

Property Management
JLL
Wind
Material Supplier

Material Supplier refers to organizations which supplied significant systems/materials for a building project (e.g. elevator suppliers, facade suppliers, etc).

Cladding
Owner
Current
601 W Companies
Past
Amoco Corporation; Piedmont Office Realty Trust; The Blackstone Group L.P.
Architect
Design

Usually involved in the front end design, with a "typical" condition being that of a leadership role through either Schematic Design or Design Development, and then a monitoring role through the CD and CA phases.

Edward Durell Stone & Associates; Perkins+Will
Structural Engineer
Design

The Design Engineer is usually involved in the front end design, typically taking the leadership role in the Schematic Design and Design Development, and then a monitoring role through the CD and CA phases.

MEP Engineer
Design

The Design Engineer is usually involved in the front end design, typically taking the leadership role in the Schematic Design and Design Development, and then a monitoring role through the CD and CA phases.

Cosentini Associates; Economy Mechanical Industries, Inc.
Contractor
Main Contractor

The main contractor is the supervisory contractor of all construction work on a project, management of sub-contractors and vendors, etc. May be referred to as "Construction Manager," however, for consistency CTBUH uses the term "Main Contractor" exclusively.

Other Consultant

Other Consultant refers to other organizations which provided significant consultation services for a building project (e.g. wind consultants, environmental consultants, fire and life safety consultants, etc).

Property Management
JLL
Wind
Material Supplier

Material Supplier refers to organizations which supplied significant systems/materials for a building project (e.g. elevator suppliers, facade suppliers, etc).

Cladding
Alberto Bufalini Successori Ltd.; Cupples

CTBUH Initiatives

Top Company Rankings: The World’s 100 Tallest Buildings

13 October 2016 - CTBUH Research

Warm Weather Spaces Walking Tours 2015

17 September 2015 - Event

Research

30 January 2020

The Global Tall Building Picture: Impact of 2019

CTBUH Research

In 2019, 126 buildings of 200 meters’ height or greater were completed. This was a 13.7 percent decrease from 146 in 2018. The total number...

About Aon Center

Located in downtown Chicago overlooking Millennium and Grant Parks on the eastern edge of the Loop. The Aon Center is one of the “string of pearl” buildings that stand-out on Chicago’s skyline for their remarkable height. At the time of its completion, the building was only the sixth supertall tower ever constructed. Originally clad in Carrara marble, it was the tallest marble-clad building in the world until it was reclad in white granite due to safety concerns in the early 1990s.

Simple in design, the Aon Center appears monolithic, without any setbacks or adornments. The building’s shape and scale are reminiscent of New York’s original World Trade Center buildings, its architectural contemporaries. Similar to the World Trade Center towers, the Aon Center 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. The columns also house piping and utility lines, eliminating the need for interior column chases that so often deprive buildings of valuable office space. They also serve to emphasize the building’s height and augment its vertical prominence.

Despite the building’s imposing configuration, it is still well-integrated into its urban habitat. The Pedway, a series of underground pedestrian walkways, connects the Aon Center to numerous surrounding buildings throughout the loop. A plaza decorated with fountains and ample seating envelops the tower on all sides and provides an inviting place for pedestrians to congregate on a nice day. Taken together, the Aon Center’s quiet, dignified façade and its simplicity overall, make it a unique and memorable addition to the skyline.

30 January 2020

The Global Tall Building Picture: Impact of 2019

CTBUH Research

In 2019, 126 buildings of 200 meters’ height or greater were completed. This was a 13.7 percent decrease from 146 in 2018. The total number...

01 March 2018

Dynamic Interrelationship between the Evolution of the Structural Systems and Façade Design in Tall Buildings

Kyoung Sun Moon, Yale University School of Architecture

The emergence of tall buildings in the late 19th century was possible by using new materials and separating the role of structures and that of...

13 October 2016

The Council is pleased to announce the Top Company Rankings for numerous disciplines as derived from the list of projects appearing in 100 of the World’s Tallest Buildings.

17 September 2015

Warm Weather Spaces Walking Tours 2015

The CTBUH Urban Habitat / Urban Design Committee organized guided walking tours of 16 cities around the globe, focusing on urban habitats around tall buildings.

29 January 2015

Seven Cities Winter Spaces Walking Tour

The new CTBUH Urban Habitat / Urban Design Committee organized a highly successful Winter Spaces Walking Tour in seven cities around the world.