The United States leads the world both in terms of the total volume of temporary staffing and recruitment services and the number of staffing companies. The country generates over $180 billion in this industry every year, with thousands of different staffing agencies operating across the USA. 

From small family-owned shops with a history of decades to multinational corporations with a presence in dozens of countries, America’s staffing companies provide millions of temporary, contract, and even permanent workers to the country’s businesses every year. 

With the healthcare, IT, finance, and light industry sectors in particular constantly in need of qualified employees, staffing companies play a crucial role in the American economy.

Below is a brief overview of the 10 largest staffing companies in the United States, ranked according to their yearly turnover, date of foundation, ownership structure, and the range of services they provide.

Quick Comparison

Rank	Company	Founded	Owner / Founders	Headquarters	Core Focus
1	Allegis Group	1983	Jim Davis & Steve Bisciotti (Founders); Andy Hilger (CEO); privately held	Hanover, Maryland	Multi-brand Staffing & Talent Solutions
2	Robert Half	1948	Founded by Robert Half; publicly listed (NYSE: RHI)	Menlo Park, California	Professional & Specialized Staffing
3	ManpowerGroup	1948	Founded by Elmer Winter & Aaron Scheinfeld; publicly listed (NYSE: MAN)	Milwaukee, Wisconsin	Workforce Solutions & Staffing
4	Kelly Services	1946	Founded by William Russell Kelly; publicly listed (NASDAQ: KELYA)	Troy, Michigan	Staffing & Workforce Solutions
5	Adecco USA	Parent formed 1996 (roots to 1957)	Part of The Adecco Group, Switzerland; publicly listed	Jacksonville, Florida	Staffing & Workforce Solutions
6	Randstad USA	Parent founded 1960	Part of Randstad NV, Netherlands; publicly listed	Atlanta, Georgia / Netherlands HQ	Recruitment & HR Services
7	Insight Global	2001	Bert Bean & Harold Bean (Co-founders)	Atlanta, Georgia	IT & Professional Staffing
8	Kforce	1962	Founded by David Dunkel & Elliott Bloom; publicly listed (NASDAQ: KFRC)	Tampa, Florida	Technology & Finance Staffing
9	Aya Healthcare	2001	Founded by Alan Braynin; privately held	San Diego, California	Healthcare Staffing
10	CHG Healthcare	1979	Employee-owned	Salt Lake City, Utah	Locum Tenens & Healthcare Staffing

1. Allegis Group – America’s Largest Privately Held Staffing Firm

• Founded: 1983 
• Owner: Founded by Jim Davis and Steve Bisciotti; privately held, led by CEO Andy Hilger 
• Headquarters: Hanover, Maryland

Allegis Group started life in a basement office as Aerotek, a firm focused on placing engineers in the aerospace and defense industries. Over four decades, it grew into a multi-brand talent powerhouse that now includes TEKsystems, Aerotek, Actalent, Aston Carter, and Major, Lindsey & Africa, among others.

It is widely recognized by Staffing Industry Analysts as the largest privately held staffing company in the United States, generating well over $10 billion in annual revenue across its network of specialized brands.

What Allegis Group does: Multi-brand staffing, workforce management, and talent solutions across IT, engineering, life sciences, and legal.

Services: IT and technical staffing, engineering and scientific staffing, executive and legal search, managed services programs (MSP), and recruitment process outsourcing (RPO).

2. Robert Half – The World’s First Specialized Staffing Firm

• Founded: 1948 
• Owner: Founded by Robert Half; publicly listed (NYSE: RHI) 
• Headquarters: Menlo Park, California

Robert Half was founded in 1948 by its namesake and is considered the world’s first and largest specialized staffing firm. It built its reputation placing accounting and finance professionals before expanding into technology, legal, and administrative staffing.

The company has repeatedly ranked among Forbes’ Best Professional Recruiting Firms and reports billions of dollars in annual revenue, with a global network of offices across North America, Europe, and Asia-Pacific.

What Robert Half does: Specialized professional staffing and consulting across finance, technology, legal, and administrative fields.

Services: Accounting and finance staffing, technology staffing, legal and administrative staffing, and executive search through its Robert Half Executive Search practice.

3. ManpowerGroup – A Global Workforce Solutions Pioneer

• Founded: 1948 
• Owner: Founded by Elmer Winter and Aaron Scheinfeld; publicly listed (NYSE: MAN) 
• Headquarters: Milwaukee, Wisconsin

ManpowerGroup was founded in Milwaukee in 1948 and has since grown into one of the largest workforce solutions companies in the world, with a presence in around 75 countries. In the US, its Manpower brand consistently ranks among the top temporary staffing firms in Forbes’ annual surveys.

Its portfolio includes Manpower for staffing, Experis for IT and professional talent, and Talent Solutions for RPO and workforce consulting.

What ManpowerGroup does: Workforce staffing, talent development, and outsourcing solutions across industries.

Services: Temporary and permanent staffing, IT and professional staffing (Experis), recruitment process outsourcing, and career transition and talent development programs.

4. Kelly Services – One of America’s Oldest Staffing Companies

• Founded: 1946 
• Owner: Founded by William Russell Kelly; publicly listed (NASDAQ: KELYA) 
• Headquarters: Troy, Michigan

Kelly Services is often credited with pioneering the modern staffing industry, having placed some of the first “temp” workers in American offices in the 1940s. The term “Kelly Girl” became a household reference to temporary office staff for decades afterward.

Today, Kelly has evolved into a broad workforce solutions company with specialized practices spanning science, engineering, education, and outsourcing and consulting.

What Kelly Services does: Staffing, workforce management, and specialty talent solutions.

Services: Professional and industrial staffing, science and engineering staffing, education staffing, and outsourcing and consulting services (KellyOCG).

5. Adecco USA – The American Arm of the World’s Largest Staffing Group

• Founded: Parent company formed in 1996 (with roots to Adia, founded 1957) 
• Owner: Part of The Adecco Group, Switzerland; publicly listed 
• Headquarters: Jacksonville, Florida

Adecco Group was formed through the 1996 merger of Swiss firm Adia and French firm Ecco, creating what is today one of the largest staffing organizations in the world. Its US operations, headquartered in Jacksonville, Florida, serve thousands of businesses with general and specialized staffing needs.

Adecco USA’s reach spans industrial, office, and professional staffing, backed by the global scale and technology infrastructure of its Swiss parent.

What Adecco USA does: General and specialized staffing and workforce management for US businesses.

Services: Temporary and permanent staffing, RPO services, payroll outsourcing, and career transition and outplacement support.

6. Randstad USA – A Global Recruitment Leader with Deep US Roots

• Founded: Parent company Randstad NV founded in 1960 
• Owner: Part of Randstad NV, Netherlands; publicly listed 
• Headquarters: Atlanta, Georgia (US) / Netherlands (Global HQ)

Randstad NV was founded in the Netherlands in 1960 by Frits Goldschmeding and has grown into one of the largest HR services companies in the world. Its US business, Randstad USA, offers staffing and workforce solutions across a wide range of sectors, from manufacturing and logistics to finance and technology.

Randstad’s global scale allows it to combine local recruiting expertise with international workforce data and technology platforms.

What Randstad USA does: Recruitment, staffing, and workforce consulting across multiple industries.

Services: Staffing and recruitment services, RPO, workforce planning and analytics, and specialized IT and engineering staffing through its Randstad Digital and Randstad Sourceright brands.

7. Insight Global – A Fast-Growing Leader in IT Staffing

• Founded: 2001 
• Owner: Founded by Bert Bean and Harold Bean; privately held 
• Headquarters: Atlanta, Georgia

Insight Global was founded in 2001 and has grown rapidly to become one of the largest IT and professional staffing firms in the country, with billions of dollars in annual US staffing revenue and a client base spanning Fortune 1000 companies.

The company operates from dozens of offices across the US and abroad, focusing heavily on quickly standing up technical teams for enterprise clients.

What Insight Global does: IT and professional staffing for large enterprises and government clients.

Services: IT staff augmentation, engineering and finance staffing, government and cleared staffing solutions, and direct-hire recruitment.

8. Kforce – A Specialist in Technology and Finance Staffing

• Founded: 1962 
• Owner: Founded by David Dunkel and Elliott Bloom; publicly listed (NASDAQ: KFRC) 
• Headquarters: Tampa, Florida

Kforce has built a strong reputation in technology and finance/accounting staffing over more than six decades in business. It is publicly traded and known for combining specialized recruiters with data-driven matching technology to serve mid-sized and enterprise clients.

The firm has carved out a particularly strong niche in the Southeast US and in fintech-adjacent technology roles.

What Kforce does: Specialized staffing and solutions in technology and finance/accounting.

Services: IT staffing and consulting, finance and accounting staffing, project-based technology solutions, and direct-hire placement.

9. Aya Healthcare – A Leader in Healthcare Staffing

• Founded: 2001 
• Owner: Founded by Alan Braynin; privately held 
• Headquarters: San Diego, California

Aya Healthcare was founded in 2001 and has grown into one of the largest healthcare staffing companies in the US, supplying travel nurses, allied health professionals, and locum tenens providers to hospitals and health systems nationwide.

The company has invested heavily in its own workforce technology platform to help healthcare facilities manage staffing shortages more efficiently, particularly during periods of high demand.

What Aya Healthcare does: Healthcare workforce staffing and management technology.

Services: Travel nursing staffing, allied health staffing, locum tenens placement, and healthcare workforce management software.

10. CHG Healthcare – A Pioneer of Employee-Owned Healthcare Staffing

• Founded: 1979 
• Owner: Employee-owned 
• Headquarters: Salt Lake City, Utah

CHG Healthcare was founded in 1979 and has grown into one of the largest healthcare staffing organizations in the country, distinguished by its employee-owned structure rather than private equity or public ownership. It operates through well-known brands such as CompHealth and Weatherby Healthcare.

CHG has been recognized repeatedly on “Best Places to Work” lists, which the company attributes in part to its employee-ownership model and long-term focus on culture.

What CHG Healthcare does: Locum tenens and permanent healthcare staffing.

Services: Physician and advanced practice staffing, locum tenens placement, permanent physician search, and allied health staffing.

Frequently Asked Questions (FAQs)

1. Which is the oldest staffing company on this list?

Kelly Services, founded in 1946, is the oldest company on this list and is widely credited with helping pioneer the modern American staffing industry.

2. Which staffing companies on this list are US-origin versus international?

Allegis Group, Robert Half, ManpowerGroup, Kelly Services, Insight Global, Kforce, Aya Healthcare, and CHG Healthcare were all founded and are headquartered in the US, while Adecco and Randstad are international staffing groups with major US operations.

3. Which company is the largest privately held staffing firm in the US?

Allegis Group, the parent company of brands such as TEKsystems and Aerotek, is widely recognized as the largest privately held staffing company in the United States.

4. Which companies specialize specifically in healthcare staffing?

Aya Healthcare and CHG Healthcare are the two companies on this list that focus specifically on healthcare staffing, including travel nursing and locum tenens placement.

5. Which companies on this list are publicly listed?

Robert Half, ManpowerGroup, Kelly Services, and Kforce are publicly traded on US stock exchanges, while the parent companies of Adecco and Randstad are listed on European exchanges.

6. What is the difference between a general staffing company and a specialist staffing firm?

General staffing companies place candidates across a broad range of roles and industries, while specialist firms such as Kforce or Aya Healthcare focus deeply on specific sectors, such as technology, finance, or healthcare.

7. Which company has an employee-ownership structure?

CHG Healthcare is notable for having an employee-ownership structure rather than being publicly traded or traditionally controlled by founders or private investors.

8. What role has the healthcare staffing sector played in recent years?

Hospital staffing shortages and rising demand for travel nurses and locum tenens providers have made healthcare one of the important and high-revenue segments of the US staffing industry.

9. How do global staffing firms like Adecco and Randstad differ from US-origin firms?

Global staffing firms such as Adecco and Randstad bring international scale, cross-border workforce expertise, and multinational client relationships, while US-origin firms often offer deep local market knowledge and long-standing brand recognition across specific American industries.

10. Why has the US staffing industry grown so much in recent years?

Growth in the US staffing industry has been driven by increasing demand for flexible and contract labor, ongoing skills shortages in areas such as IT and healthcare, and employers increasingly relying on staffing companies to improve hiring speed and manage workforce needs.

Conclusion

America’s staffing industry is as varied and sprawling as the US economy itself. It ranges from established staffing giants like Kelly Services and Robert Half, which were among the first to popularize executive searches and placed thousands of employees in the workplace many decades ago, to more modern and specific staffing specialists, such as Aya Healthcare or Insight Global.

The US staffing and recruiting industry is worth hundreds of billions of dollars, and the demand for its services is growing every year. As such, the ten staffing companies discussed in this presentation will continue to shape and influence America’s hiring practices in the years to come.