Aon Center

Introduction: A Landmark in Chicago’s Skyline

The Aon Center is a defining feature of Chicago’s East Loop, soaring at 200 East Randolph Street. Originally constructed in 1973 as the Standard Oil Building, this skyscraper, designed by Edward Durell Stone and the Perkins & Will Partnership, exemplifies International Style modernism, a movement that shaped the city’s architectural legacy (WikiArquitectura; Buildings DB). Rising 1,136 feet over 83 floors, the Aon Center was once Chicago’s tallest building and the fourth tallest globally (Britannica; Tallest Building). Over the decades, the building has borne witness to engineering challenges, significant renovations, and a shifting business landscape, all while remaining a vital and accessible destination for both visitors and locals.

This guide provides an in-depth look at the Aon Center’s history, architectural innovations, visitor information, sustainability efforts, and tips for making the most of your time in the surrounding area. Whether you’re an architecture enthusiast, a tourist, or a business traveler, you’ll find everything you need to plan your visit.

Origins and Construction

The Aon Center’s construction began in 1970, culminating in 1973 as the new headquarters for the Standard Oil Company of Indiana (WikiArquitectura; Wikipedia). Designed by Edward Durell Stone with Perkins & Will, the building exemplified the International Style through its minimalist, rectilinear form and innovative structural approach (Buildings DB; Art Facts).

Architectural Style and Structural Innovations

The Aon Center features a framed tube structure—a system of closely spaced perimeter columns connected by deep spandrel beams, allowing for column-free, flexible interior spaces (WikiArquitectura). Originally, its façade was clad with 44,000 thin slabs of white Carrara marble sourced from Tuscany, reflecting classical elegance and modern innovation (Britannica).

Facade Failure and Recladding

The building’s marble façade soon proved problematic. Chicago’s climate caused thermal expansion and contraction, resulting in the marble panels bowing and cracking (Medium). In 1973, a marble slab fell, highlighting the risk. By 1985, significant deterioration mandated action. Temporary steel straps were installed, but ultimately, the marble was replaced with durable white granite in the early 1990s, at a cost of $80 million (WikiArquitectura; Medium).

Name Changes and Tenancy

Initially the Standard Oil Building, it became the Amoco Building in 1985, reflecting the company’s new identity, and was renamed Aon Center in 1998 for its anchor tenant, Aon Corporation (Wikipedia; Britannica). The building is a major hub for corporate tenants including Blue Cross Blue Shield Association and Kraft Heinz (Wikipedia).

Place in Chicago’s Skyline

The Aon Center remains one of Chicago’s tallest and most recognizable skyscrapers—third tallest as of 2025—characterized by its vertical white granite façade and minimalist aesthetic (Art Facts; Tallest Building). Its design is often compared to New York’s former World Trade Center towers, emphasizing clean lines and structural clarity (WikiArquitectura).

Visiting the Aon Center: Practical Information

Visiting Hours and Tickets

• Lobby Access: Open to the public Monday–Friday, 7:00 AM–7:00 PM. Limited or no access on weekends and holidays.
• Tickets: No tickets required for lobby or retail area access. There is no regular public observation deck.

Guided Tours

While the Aon Center does not offer its own public tours, local organizations like the Chicago Architecture Foundation include exterior stops as part of broader architectural walking tours.

Accessibility

The building is fully ADA-compliant, with accessible entrances, elevators, and restrooms. Exterior plazas and public spaces are wheelchair accessible.

Nearby Attractions

• Millennium Park: Directly adjacent, featuring Cloud Gate ("The Bean").
• Art Institute of Chicago: Short walk away.
• Grant Park, Maggie Daley Park, Chicago Cultural Center, and Lake Michigan: All within easy walking distance.
• Chicago Lakefront Trail: Ideal for photography and city views.

Travel Tips

• Transit: Connected to the Pedway system and near CTA and Metra stations.
• Parking: Available but can be expensive; public transit is recommended.
• Photography: Best exterior shots at sunrise or sunset from Millennium Park or the lakefront.

Amenities and Facilities

• Lobby & Common Areas: Modern, inviting, and renovated, with retail and dining options (Telos Group).
• Cloud Level (70th Floor): Highest amenity space in Chicago, generally not open to the public except for special events.
• Outdoor Plaza: Landscaped seating and gathering areas extend Millennium Park to the Aon Center’s entrance.

Navigating the Pedway

• Access: Entrances from the building’s lower levels with signage.
• Wayfinding: Look for Pedway maps and symbols; digital maps are available online.
• Features: Public art, food courts, and retail along the route.

Sustainability and Modernization

The Aon Center employs energy-efficient systems, green features, and sustainable commuting facilities. Recent upgrades ensure compliance with modern environmental standards and contribute to Chicago’s sustainability goals (Tallest Building; Telos Group).

Frequently Asked Questions (FAQ)

Q: Does the Aon Center have a public observation deck or tours?
A: No regular public observation deck or interior tours. Special events may occasionally offer access to upper floors.

Q: What are the visiting hours?
A: Monday–Friday, 7:00 AM–7:00 PM for lobby access.

Q: Is there an admission fee?
A: No. Lobby and exterior access are free.

Q: Is the building accessible?
A: Yes. Fully ADA-compliant.

Q: How do I get there on public transit?
A: Connected via the Pedway to CTA and Metra stations. Multiple bus routes nearby.

Q: What are the best times for photography?
A: Early morning and late afternoon for optimal lighting.

Visuals and Interactive Media

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• Interactive map of Aon Center and nearby attractions