Interior design shapes how offices, hospitals, airports, and homes look and feel every day. A small group of large design firms handle most of the biggest interior design projects across the United States.
Some of these companies started over a century ago as small architecture firms. Others focused only on interiors from the very beginning and grew into global names over time.
In this article, we’ll discuss the top 10 interior design companies in the United States, based on their history, ownership, and the kind of projects they are known for.
Quick Comparison
| Rank | Company | Founded | Owner / Founders | US Headquarters | Core Focus |
| 1 | Gensler | 1965 | Founded by Art Gensler, Drue Gensler & James Follett; privately held, led by Co-CEOs Jordan Goldstein & Elizabeth Brink | San Francisco, California | Workplace & Commercial Interiors |
| 2 | HOK | 1955 | Founded by George Hellmuth, Gyo Obata & George Kassabaum; privately held | St. Louis, Missouri | Healthcare & Corporate Interiors |
| 3 | Perkins&Will | 1935 | Founded by Lawrence Perkins & Philip Will Jr.; owned by Sidara | Chicago, Illinois | Healthcare, Education & Workplace Design |
| 4 | HDR | 1917 | Founded as Henningson, Durham and Richardson; employee-owned | Omaha, Nebraska | Healthcare & Institutional Interiors |
| 5 | IA Interior Architects | 1984 | Founded by David Mourning; privately held, led by Co-CEO Tom Powers | San Francisco, California | Corporate Workplace Interiors |
| 6 | CallisonRTKL | 2015 (roots to 1975) | Formed from Callison and RTKL; owned by Arcadis | Baltimore, Maryland | Retail, Hospitality & Workplace Interiors |
| 7 | Corgan | 1938 | Founded by Jack Corgan; privately held | Dallas, Texas | Aviation, Workplace & Healthcare Interiors |
| 8 | HKS Inc | 1939 | Founded by Harwood K. Smith; privately held, led by CEO Heath May | Dallas, Texas | Sports, Healthcare & Hospitality Interiors |
| 9 | Skidmore, Owings & Merrill (SOM) | 1936 | Founded by Louis Skidmore & Nathaniel Owings; privately held | Chicago, Illinois | High-Rise & Corporate Interiors |
| 10 | Mancini Duffy | 1896 | Founded by Anthony Mancini’s predecessor firm; privately held | New York, New York | Workplace, Retail & Education Interiors |
1. Gensler – The World’s Largest Design Firm
- Founded: 1965
- Owner: Founded by Art Gensler, Drue Gensler & James Follett; privately held, led by Co-CEOs Jordan Goldstein & Elizabeth Brink
- Headquarters: San Francisco, California
Art Gensler, his wife Drue, and their colleague James Follett founded Gensler in 1965, initially focusing on corporate office interiors. Their early projects included interiors for major San Francisco office towers built in the late 1960s. That early focus on workplace design still shapes much of Gensler’s work today.
The firm has grown into the largest architecture and design company in the world by revenue. Andy Cohen and Diane Hoskins led the firm for nearly 20 years before becoming global co-chairs in 2024. Jordan Goldstein and Elizabeth Brink now serve as co-CEOs, running day-to-day operations.
What Gensler does: Designs offices, interiors, and buildings for companies and institutions worldwide.
Services: Workplace interior design, architecture, brand design, and urban planning.
2. HOK – A Firm Known for Healthcare and Corporate Spaces
- Founded: 1955
- Owner: Founded by George Hellmuth, Gyo Obata & George Kassabaum; privately held
- Headquarters: St. Louis, Missouri
HOK was founded in 1955 by three architects who wanted to combine architecture, engineering, and interior design under one roof. This unusual full-service approach was uncommon in the design industry at the time. The firm quickly built a reputation for large, complex projects like hospitals and sports arenas.
HOK grew into one of the largest design firms in the world, with offices spread across multiple countries. The company remains especially known for its work in healthcare, corporate, and technology-focused interiors. HOK continues to be privately owned by its senior leadership team today.
What HOK does: Designs interiors, architecture, and planning for hospitals, offices, and public spaces.
Services: Healthcare interior design, corporate interiors, architecture, and urban planning.
3. Perkins&Will – A Chicago Firm Focused on Human Well-Being
- Founded: 1935
- Owner: Founded by Lawrence Perkins & Philip Will Jr.; owned by Sidara
- Headquarters: Chicago, Illinois
Perkins&Will was started in 1935 by two Cornell University classmates, Lawrence Perkins and Philip Will Jr., in Chicago. The firm gained early national attention for a school design that focused heavily on natural light and child well-being. That same focus on health and comfort has stayed central to the firm’s design philosophy.
In 1986, the firm became part of Sidara, a large international design and engineering group. Perkins&Will has since grown through acquisitions of other design firms across the US. The company today is especially known for healthcare, education, and workplace interior projects.
What Perkins&Will does: Designs interiors focused on health, comfort, and sustainability.
Services: Healthcare interior design, education design, workplace interiors, and architecture.
4. HDR – An Employee-Owned Firm With Deep Healthcare Roots
- Founded: 1917
- Owner: Founded as Henningson, Durham and Richardson; employee-owned
- Headquarters: Omaha, Nebraska
HDR traces its roots back to 1917, starting under the name Henningson, Durham and Richardson before later shortening to HDR. The firm built its early reputation on engineering and infrastructure projects across the Midwest. Over time, HDR expanded into full interior design services alongside its engineering work.
The company today is owned by its own employees rather than outside investors. HDR is especially known for designing hospitals, research labs, and other institutional buildings. The firm continues combining engineering expertise with detailed interior design work.
What HDR does: Designs interiors for hospitals, research facilities, and institutional buildings.
Services: Healthcare interior design, engineering, architecture, and facility planning.
5. IA Interior Architects – The First Firm Built Only for Interiors
- Founded: 1984
- Owner: Founded by David Mourning; privately held, led by Co-CEO Tom Powers
- Headquarters: San Francisco, California
IA Interior Architects was started in 1984 by David Mourning, who built the firm around a fairly radical idea at the time. Instead of offering full architecture services, IA chose to focus entirely on interior spaces. This made it the first global architecture firm dedicated only to interiors.
Mourning led the company for 32 years before stepping back from daily leadership in 2014. Tom Powers now serves as co-president and CEO, continuing the firm’s interior-only focus. IA Interior Architects mainly works with large corporations on office and workplace design.
What IA Interior Architects does: Designs office and workplace interiors exclusively, without full architecture services.
Services: Workplace interior design, strategic space planning, and corporate design consulting.
6. CallisonRTKL – A Merger of Two Major Design Firms
- Founded: 2015 (roots to 1975)
- Owner: Formed from Callison and RTKL; owned by Arcadis
- Headquarters: Baltimore, Maryland
CallisonRTKL’s history traces back to Callison, a Seattle firm founded in 1975 that became known for retail and hospitality design. Dutch engineering company Arcadis bought Callison in 2014, then merged it with another of its firms, RTKL, in 2015. This combination created one large design firm covering retail, hospitality, and workplace interiors.
The merged company kept both original names, becoming CallisonRTKL, based out of Baltimore, Maryland. Arcadis continues to own the firm as part of its larger global design and engineering business. CallisonRTKL remains especially known for shopping malls, hotels, and mixed-use interior projects.
What CallisonRTKL does: Designs interiors for retail stores, hotels, and mixed-use developments.
Services: Retail interior design, hospitality design, workplace interiors, and architecture.
7. Corgan – A Dallas Firm Known for Airports and Workplaces
- Founded: 1938
- Owner: Founded by Jack Corgan; privately held
- Headquarters: Dallas, Texas
Corgan was started in Dallas over 80 years ago by architect Jack Corgan, focusing at first on general architecture projects across Texas. The firm later built a specialty in airport design, working on major terminals across the country. That aviation expertise became one of Corgan’s biggest strengths over time.
Corgan expanded well beyond airports into corporate workplace and healthcare interior design as well. The firm remains privately owned and headquartered in Dallas today. Corgan continues to be one of the most active design firms working on large US airport projects.
What Corgan does: Designs interiors for airports, offices, and healthcare facilities.
Services: Aviation interior design, workplace interiors, healthcare design, and architecture.
8. HKS Inc – A Texas Firm Known for Stadiums and Hospitals
- Founded: 1939
- Owner: Founded by Harwood K. Smith; privately held, led by CEO Heath May
- Headquarters: Dallas, Texas
HKS was founded in 1939 by architect Harwood K. Smith in Dallas, Texas, initially focused on general building design. The firm later became especially known for designing massive sports stadiums used by NFL and other major teams. Projects like AT&T Stadium and SoFi Stadium helped build HKS’s national reputation.
Alongside stadiums, HKS also grew a strong healthcare and hospitality design practice over the decades. Heath May now leads the company as CEO, overseeing projects across multiple design sectors. HKS remains privately owned and headquartered in its original home city of Dallas.
What HKS Inc does: Designs interiors for sports venues, hospitals, and hotels.
Services: Sports venue interior design, healthcare design, hospitality interiors, and architecture.
9. Skidmore, Owings & Merrill (SOM) – A Firm Known for Iconic Towers
- Founded: 1936
- Owner: Founded by Louis Skidmore & Nathaniel Owings; privately held
- Headquarters: Chicago, Illinois
SOM was started in Chicago in 1936 by Louis Skidmore and Nathaniel Owings, with engineer John Merrill joining a few years later. The firm quickly became known for clean, modern building designs during a time of major American growth. SOM’s work included interiors for some of the tallest buildings ever constructed.
The firm has designed interiors and structures for landmark skyscrapers across major US cities for decades. SOM remains privately owned by its partners rather than outside investors. The company continues focusing heavily on high-rise buildings and large corporate interior projects.
What SOM does: Designs interiors and architecture for skyscrapers and major corporate buildings.
Services: High-rise interior design, corporate workplace design, architecture, and urban planning.
10. Mancini Duffy – One of America’s Oldest Design Firms
- Founded: 1896
- Owner: Traces back to a founding New York architecture practice; privately held
- Headquarters: New York, New York
Mancini Duffy was established in 1896, which makes it one of the oldest design firms in America. Since its foundation, the company has experienced numerous design trends’ cycles, which have enriched the firm with vast experience in different areas of design.
Today, Mancini Duffy focuses on corporate, retail, and educational interior design. As an old-established design company, Mancini Duffy has significant experience in the field. Mancini Duffy has also invested in new design technologies, such as virtual reality. The company is based in New York City, where it has been headquartered since its foundation.
What Mancini Duffy does: Designs interiors for offices, retail stores, and schools.
Services: Workplace interior design, retail design, education design, and architecture.
Frequently Asked Questions (FAQs)
1. Which is the largest interior design company in the USA?
Gensler is the largest design firm in the US by revenue, known especially for workplace and commercial interior design.
2. Which is the oldest interior design company on this list?
Mancini Duffy is the oldest, tracing its history back to 1896 in New York City.
3. Which firm focuses only on interior design, without full architecture services?
IA Interior Architects was the first global firm built to focus entirely on interiors rather than full architecture.
4. Which firm is best known for sports stadium design?
HKS Inc is best known for designing major sports stadiums, including several large NFL venues.
5. Which firm is owned by employees rather than outside investors?
HDR is owned by its own employees, rather than by outside shareholders or a parent company.
6. Which firm is known for airport design?
Corgan is especially known for designing major airport terminals across the United States.
7. Are interior design firms in the USA regulated?
Yes, many design projects must follow local building codes, and licensed architects on staff must meet state licensing requirements.
8. Which firm was formed by merging two older companies?
CallisonRTKL was formed by merging Callison and RTKL, two design firms both owned by Arcadis.
9. Which firm is known for designing tall skyscrapers?
Skidmore, Owings & Merrill (SOM) is especially known for designing interiors and structures for some of the world’s tallest buildings.
10. Why do these ten companies matter to everyday people?
These companies design the offices, hospitals, airports, and stores that millions of Americans use every single day.
Conclusion
America’s top interior design companies comprise century-old architectural design firms and those that were formed to specialize in design of interiors exclusively. Thus, Gensler, HOK, Perkins&Will, HDR, Corgan, HKS, SOM, and Mancini Duffy were all founded in the United States. Meanwhile, IA Interior Architects is known to have pioneered the design of interiors.
These ten companies are responsible for the design of millions of square feet of commercial and medical facilities, including offices, hospitals, airports, and retail stores throughout the United States. As the workplace and public space design trends continue to evolve, these interior design companies will continue to shape the American environment for years to come.
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