Many of the largest companies are also household names — but not all. While often the largest public companies are recognizable, some of the largest private companies are far less known. For example, privately owned Cargill, a large conglomerate heavily involved in agricultural and food production, had revenues of nearly $135 billion in 2014. This was more than the 2014 revenue of widely known and public AT&T of about $132.4 billion.

Based on data from PrivCo, 24/7 Wall St. reviewed the 20 private companies with the largest revenues. All of these companies had revenues of at least $20 billion, with Koch Industries and Cargill Incorporated reporting revenues well over $100 billion, the two highest. The companies employ between 5,000 and 200,000 workers each, with Ernst & Young employing the most workers at roughly 200,000.

Click here to see America’s 20 largest private companies

These companies do not have much in common beyond being privately held and often also being quite old. Several of the companies were founded in the 1800s or early 1900s. Cargill, the largest private company, is also one of the nation’s oldest, founded in 1865 at the end of the Civil War. The size of these companies is often the result of success compounded over decades, leading them to become dominant players in their respective industries.

In an interview with 24/7 Wall St., Radek Jagielski, Senior Analyst at PrivCo, explained how large capital bases accumulated over many years are a major advantage for these companies. With so many resources available for investment, “there’s really no reason for them to go public and dilute their ownership, ” said Jagielski. In addition, Jagielski explained, large capital bases can be used to “acquire competitors before they become real threats.”

Many of the oldest companies on the list are family owned businesses, with namesakes still held by current owners. In several cases, family members have retained an active role in the management of the company. For example, Bechtel, one of the world’s largest construction and engineering contractors, is chaired by Riley Bechtel, while Brendan Bechtel is the company’s president and COO.

In all cases, the families’ retention of control of these large companies has resulted in extraordinary inherited wealth. For example, the Koch brothers, who control Koch Industries, are estimated to be worth more than $40 billion each.

Many of the largest private companies are mutual insurance companies. These are insurance companies that are set up to be owned by their policyholders, and so are inherently private companies. These companies, such as State Farm Mutual and Health Care Service Corporation are among the largest insurance companies in the nation.

Policyholders at these insurance companies have voting rights and do not have to worry about being taken over. According to Jagielski, this means these companies can make more long-term strategic plans. In addition, he said, policyholders are able to make changes when they’re unhappy with the insurance product. Less access to capital is one disadvantage to this model. However, as all of the insurance companies on this list have been around for nearly 100 years or more, access to capital is not a major issue.

To identify the largest private companies, 24/7 Wall St. reviewed the 100 U.S. private companies with the largest annual revenue figures from PrivCo. Revenues are as of the most recent period available. Company headcounts, headquarter locations, and the industries in which the companies operate also come from PrivCo. Financial data and company histories come from company websites.

These are 20 largest private companies.

20. Love’s Travel Stops & Country Stores, Inc.
> Revenue: $22.65 billion
> Number of employees: 10,500
>Headquarters: Oklahoma City, Oklahoma
> Industry: Retail

Love’s Travel Stops & Country Stores was started by Tom and Judy Love in 1964 with a single gas station in Watonga, Oklahoma. Today, the company has more than 330 locations in 39 states. The company is still run by family members, and Tom Love remains its CEO. Forbes estimates that Tom and Judy Love have a combined net worth of $4.1 billion, largely due to their control of the company.

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19. Reyes Holdings LLC
> Revenue: $23 billion
> Number of employees: 16,100
>Headquarters: Rosemont, Illinois
> Industry: Food and beer distributor

Reyes Holdings is a holding company that controls a number of food and beverage distributors operating around the world. Among the company’s largest holdings is Martin-Brower, which Reyes acquired in 1998. Martin-Brower is the largest distributor for McDonald’s, employing 7,800 people. The company is controlled by brothers Christopher and Jude Reyes, who Forbes ranks as tied for the 418th richest people in the world. Each have an estimated wealth of $4 billion.

18. Penske Corporation
> Revenue: $23.1 billion
> Number of employees: 38,848
>Headquarters: Bloomfield Hills, Michigan
> Industry: Transportation Services

Penske Corporation is a diversified transportation services company. It operates a wide range of services, including car and truck rental, car dealerships, and auto part manufacturing. The company was founded in 1969 by Roger Penske, who also owns auto racing team Penske. Penske himself was a former race car driver who once raced in both Formula One and NASCAR. The company is also very active in other countries, with more than 275 locations worldwide.

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17. Nationwide Mutual Insurance Co.
> Revenue: $23.9 billion
> Number of employees: 33,672
>Headquarters: Columbus, Ohio
> Industry: Insurance

Nationwide is one of the several policyholder-owned mutual insurance companies on our list of largest private companies in the country. Nationwide started out in 1925 as the Farm Bureau Mutual Automobile Insurance Company. Its original goal was to provide affordable auto insurance for Ohio farmers. In 1955, the company changed its name to Nationwide after having expanded to 20 states beyond Ohio. Today, the company is one of the nation’s largest insurers, ranking ninth in life insurance and seventh in homeowner’s insurance, in terms of total premiums.

16. KPMG LLP
> Revenue: $24.82 billion
> Number of employees: 162,031
>Headquarters: New York, New York
> Industry: Accounting Services

KPMG is one of the largest accounting firms in the United States. It is one of the Big Four accounting service providers in the country along with Ernst & Young, Deloitte, and PricewaterhouseCoopers. The company operates in 155 countries and employs more than 160,000 people, making it the third largest private employer on our list. Much of the increase in the size of the company has been through mergers. Most recently the company became KPMG after it merged in 1987 with Klynveld Main Goerdeler and Peat Marwick International.

15. C&S Wholesale Grocers, Inc.
> Revenue: $25.9 billion
> Number of employees: 13,200
>Headquarters: Keene, New Hampshire
> Industry: Food Distributer

C&S Wholesale Grocers is the largest grocery wholesaler in the United States, according to the company. The company operates 50 locations across 15 states, serving about 5,000 grocery stores and other customers. The company was founded in 1918 by Israel Cohen and Abraham Siegel in Worcester, Massachusetts. Rick Cohen, current CEO, is the third generation Cohen to lead the company.

14. Massachusetts Mutual Life Insurance Company
> Revenue: $26.4 billion
> Number of employees: 6,800
>Headquarters: Springfield, Massachusetts
> Industry: Insurance

Massachusetts Mutual is one of several insurance companies reporting the 20 highest private company revenues. Mutual insurance companies are owned by their policyholders, and so are private by definition. While the company does not have shareholders, its policyholders are entitled to vote as members of the Board of Directors, and in some cases eligible to receive dividend payments. Massachusetts Mutual is also quite old, founded May 15, 1851.

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13. Northwestern Mutual Life Insurance Company
> Revenue: $26.707 billion
> Number of employees: 5,500
>Headquarters: Milwaukee, Wisconsin
> Industry: Insurance

Like several of the largest private companies, Northwest Mutual is a very old company, founded in 1857. The company has over 330 offices in the United States and serves over four million clients. While the company specializes in life insurance, it offers a broad array of insurance products. The company also offers financial services to its clients, including brokerage services and retirement products.

12. Carlson Wagonlit Travel Inc.
> Revenue: $27.3 billion
> Number of employees: 20,000
>Headquarters: Minneapolis, Minnesota
> Industry: Travel Agency

Carlson Wagonlit is one of the world’s largest travel management companies, according to the company. It operates in 150 countries and generates more than $27 billion in revenue. The company was formed through a 1994 merger of two large travel agencies, Carlson Travel Network and Wagonlit Travel. The company’s oldest component dates back to 1888, when the Ask Mr. Foster travel agency was founded in St. Augustine Florida, the oldest city in the continental United States.

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11. Ernst & Young LLP
> Revenue: $27.4 billion
> Number of employees: 190,000
>Headquarters: New York, New York
> Industry: Accounting Services

Ernst & Young is one of the biggest accounting firms in the nation. It is one of the Big Four accounting firms in the country along with KPMG, Deloitte, and PricewaterhouseCoopers. The company operates on a global scale, with more than 700 offices in 150 countries. The company became one of the largest accounting firms in part due to mergers and acquisitions of smaller accounting firms. Today’s Ernst & Young is the product of a 1989 merger between Arthur Young and Ernst & Whinney. The oldest component of the company dates back to the founding of the English firm Harding & Pullein in 1849. The company is the largest private employer on our list, with 190,000 employees worldwide.

10. Publix Super Markets Inc.
> Revenue: $29.2 billion
> Number of employees: 167,367
>Headquarters: Lakeland, Florida
> Industry: Super Market Operator

Publix Super Markets is one of the nation’s largest grocery store operators and the largest employee-owned grocery store chain, according to the company. Publix is the second largest privately owned employer on our list with just under 168,000 employees. The company has 1,099 store locations, operating in five Southeastern states. Most of the locations are in Florida, where the company has 759 stores and makes up about 40% of the state’s grocery store market. The company was founded in George Jenkins in 1930.

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9. Pilot Flying J
> Revenue: $32.09 billion
> Number of employees: 21000
>Headquarters: Knoxville, Tennessee
> Industry: Retail

Pilot Travel Centers and Flying J merged in July of 2010 to create Pilot Flying J. Today, the merged companies are the largest privately-held retail gas and convenience store chain in the country. The company has 703 locations across all 50 states. The company originated from the Pilot Corporation, which was founded in 1958 when James Haslam II opened a gas station in Gate City, Virginia.

8. Mars Inc.
> Revenue: $35.25 billion
> Number of employees: 77000
>Headquarters: McLean, Virginia
> Industry: Candy and Confectionery Products Manufacturer

Mars is the world’s largest candy company. It owns some of the most popular candy brands such as Snickers, Twix, and of course the Mars bar. Part of the company’s size is attributable to acquisitions of other candy companies over the years, including Wrigley Company, which produces products such as Starburst and Skittles. The company is owned by the Mars family, whose ownership in the company makes them one of the richest families in the country.

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7. Liberty Mutual Holding Co., Inc.
> Revenue: $39.631 billion
> Number of employees: 55000
>Headquarters: Boston, Massachusetts
> Industry: Insurance

Liberty Mutual was founded in 1912 as Massachusetts Employees’ Insurance Association. Over the next several decades, the company expanded its operations to all states. Today, Liberty Mutual Holdings is the third largest property and casualty insurer in the country. Like all of the insurers on this list, Liberty Mutual is policyholder-owned.

6. Bechtel Corporation
> Revenue: $42.15 billion
> Number of employees: 53,000
>Headquarters: San Francisco, California
> Industry: Construction & Engineering

Bechtel is one of the largest diversified construction and engineering contractors in the world, working in a variety of industries including oil and gas, infrastructure and telecommunications. The company was founded in 1898 by Warren Bechtel and initially focused on railroad construction projects. Notable projects include working on building the Hoover Dam, development of the Jubail Industrial City in Saudi Arabia, and aiding in the cleanup following the Three Mile Island accident. The company is largely owned by descendants of Warren Bechtel, and the family has remained consistently involved in the company’s management.

5. Health Care Service Corporation
> Revenue: $55 billion
> Number of employees: 20,975
>Headquarters: Chicago, Illinois
> Industry: Insurance

The Health Care Service Corporation is the largest policyholder-owned health insurance company and the fourth largest overall provider of health insurance in the country, according to the company. The company was founded in 1936 by a group of Chicago doctors and subsequently expanded throughout the rest of Illinois and the nation. Today, the company provides insurance for nearly 14.7 million people. It primarily operates in Illinois, Texas, Montana, New Mexico, and Oklahoma.

4. Dell Inc.
> Revenue: $55.49 billion
> Number of employees: 110,100
>Headquarters: Round Rock, Texas
> Industry: Technology & Electronics

Dell was founded by Michael Dell in 1984, when he was still in college. The company grew into one of the largest providers of computers and servers to individuals and corporations in the world. The company went public in 1988 and became one of the largest publically-traded PC makers in the world. Dell became one of the largest privately held companies in the country after Michael Dell and private equity firm Silver Lake Partners bought back the publicly traded shares in 2013. The two parties acquired the company for $24.9 billion. The company ceased public trading on October 29, 2013.

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3. State Farm Mutual Automobile Insurance Co.
> Revenue: $71.2 billion
> Number of employees: 72,000
>Headquarters: Bloomington, Illinois
> Industry: Insurance

State Farm Mutual Automobile Insurance is the nation’s largest mutual insurance company on our list by revenue. Mutual insurance companies are owned entirely by their policyholders. The company was founded in 1922 by George Jacob “G.J.” Mecherle, a retired farmer. The firm initially catered to farmers but expanded over the years into a diversified insurance provider. The company has nearly 44 million auto insurance customers, insuring more cars than any insurer in the country, according to the company.

2. Koch Industries, Inc.
> Revenue: $121 billion
> Number of employees: 102,000
>Headquarters: Wichita, Kansas
> Industry: Diversified Conglomerate

Koch Industries was founded in 1940 as Wood River Oil and Refining Company, an energy engineering business. While it has retained its energy focus, over the past 75 years the company has evolved into a diversified global conglomerate. The company employs more than 100,000 people and operates in 60 countries. The company is largely owned by members of the Koch family. It is the source of wealth behind the large-scale conservative political activities of the Koch brothers, David and Charles.

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1. Cargill Incorporated
> Revenue: $134.872 billion
> Number of employees: 143,000
>Headquarters: Wayzata, Minnesota
> Industry: Diversified Conglomerate

Cargill is the largest privately held company in the United States by revenue. Founder W.W. Cargill started the company in 1865 in the grain business. Over the last 150 years it has grown into a massive and diversified conglomerate. While the company is still heavily involved in the agriculture and food processing businesses, it also has industrial and financial services segments. The company has 143,000 employees and operates in 67 countries. It is primarily owned by descendants of the firm’s founder. Based on its 2014 revenues of $134.9 billion if the company were publicly traded it would be 11th on the Fortune 500 list, behind Valero Energy and ahead of AT&T.

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