The richest people in America have a surprising amount in common.

For starters, theyre all men who mostly work in tech. And almost all of them made their fortunes by starting their own companies and maintaining ownership as they soared to success, including Microsoft and Facebook. In fact, seven of the 10 richest men in America are also among the 10richest people in the world.

These American billionaires also share a few quirks: Microsoft founder Bill Gates, Facebook CEO Mark Zuckerberg, Oracle founder Larry Ellison dropped out of college. Jeff Bezos, Larry Page and Sergey Brin allwent to Montessori schools, where children are encouraged to think independently and creatively rather than following traditional rules. It seems, too, that billionaires really like houses in Hawaii.

As is the case with therichest women in America, the richest people in America donate a lot of money to causes they care about. Some of the men on this list have donated hundreds of millions into research designed to improve human lifespan and eradicate dangerous diseases, such as Alzheimers disease and cancer. Warren Buffett, Gates, Zuckerberg, and Ellison have gone a step further and promised to give their fortunes away as part ofThe Giving Pledge, an initiative designed by Buffett and Gates to encourage billionaires to funnel their vast wealth to philanthropy.

Heres everything else you need to know about the richest people in America.

Bezos, 53, recently becamethe richest person in history.

Before he started selling books online, a business that ultimately became e-commerce giant , he worked at a hedge fund in New York after graduating from Princeton. The beginnings of m are typical start up lore Bezos started the company out of his garage in Seattle in 1994, according toForbes.

The Amazon.com founder is well-known for purchasing the WashingtonPostfor $250 million in 2013, but his space startup,Blue Origin,is quickly becoming nearly as famous. The aerospace company is developing re-useable rockets to carry passengers into space, with the goal of one day moving industrial manufacturing off of Earth.

Bezos lives with his wife and four children in Medina, Wash. He owns five houses, as well as a 290,000-acre ranch in Texas where Blue Origin is headquartered, making himone of the largest land holders in the U.S.He was named TIME person of the year in 1999.

Gates, 62, is an iconic entrepreneur who co-founded the software company Microsoft in 1975. Gates made his fortune primarily through his shares of the company after dropping out of Harvard.

He was raised in Seattle and met his future business partner, Paul Allen, with whom he founded Microsoft, in high school. The two became obsessed with computersand even created their first venture, a traffic data system,while still in school.

Gates became a millionaire at age 31 after Microsoft went public in 1986. In the 21st century, hes become known for his commitment to philanthropy and establishedThe Bill and Melinda Gates Foundationwith his wife, Melinda, in 2000. The largest private charity in the world, the Gates Foundation aims to solve global problems like world hunger and empower people in poor communities.

Gates currently lives in Medina, Wash., in the same neighborhood as Jeff Bezos. He was a TIME person of the year in 2005 andawarded the Presidential Medal of Freedom by Barack Obama in 2016.

Warren Buffett, chairman and CEO of Berkshire Hathaway, smiles during a Bloomberg interview in New York on Wednesday, April 23, 2014. Chris Goodney

Buffet, 87, is one of the only richest people in America not to have made his fortune in the tech industry. Known as the Oracle of Omaha, Buffet is the chairman and CEO of the publicly traded investment firm Berkshire Hathaway. Most of his wealth isderived from an 18% stakein the business. Buffet is known for being a value investor who holds stocks over long periods of time.

He boughthis first stocks at age 11, and at age $13 filed his first tax return with a $35 deduction for his bicycle.

On Jan. 10, Buffetappointed two of Berkshire Hathaways vice presidents to its board as vice chairs, a move that sparked speculation he may execute his succession plan for Berkshire Hathaway sooner rather than later, but the billionaire said the decision is a part of a movement to succession over time.

Co-Founder, Chairman and CEO of Facebook Mark Zuckerberg speaks during his keynote at the 2014 Mobile World Congress in Barcelona, Spain.

Zuckerberg, 33, is another Harvard dropout who is famous for starting his own tech company. Theres evena movieabout it. He is the co-founder and CEO of Facebook, the largest social media network in the world. When the company went public in 2012, it was the biggest tech IPO in history.

He owns an estimated$175 million worth of real estate across the country, with 700 acres of property in Hawaii alone. He usually calls Palo Alto, Calif. home, where he lives with his two daughters and wife, Priscilla Chan, whom he met at Harvard.

Together, the couple started theChan Zuckerberg Initiative, pouring$3 billion of funding into an effortto cure diseases and develop new technology for researchers. The foundation also established a Biohub at the University of Calif. San Francisco to bolster collaboration among scientists.

Larry Page, co-founder of Google Inc. and chief executive officer of Alphabet Inc., speaks during the 2015 Fortune Global Forum in San Francisco, California, U.S., on Monday, Nov. 2, 2015.

David Paul Morris – Bloomberg via Getty Images

Page, 44, is one of Googles co-founders and is now the CEO of its parent company, Alphabet. He met his business partner Sergey Brin, No. 7 on the list of richest people in America, while working on his doctorate at Stanford.

Most of Pages wealth comes from inventing one of the worlds most valuable tech companies through his stock he owns about 6% of Google. Under Page, who is known for his efficiency, Googlehas invested in hundreds of start-ups. He decided to rid himself of his assistants in 2007 so that anyone who needed him must physically find him in order to talk.

Page became fascinated with computers at a young age,picking up a passion for tech from his parents, who both taught computer science at Michigan State University.

Page resides in Palo Alto with his wife, a research scientist, and their two children.

Ellison, 73 another college dropout co-founded the software firm Oracle in 1977. In addition to owning about 25% of the company, he alsoowns the entire Hawaiian island of Lanai, a sailing team and even an entire tennis tournament, the New YorkTimesreports.

While known for living large (the billionaire owns a 288-foot yatch), Ellison started out with modest ambitions. His parents,who adopted him when he was nine months old,wanted him to be a doctor, but he left school when he realized medicine didnt interest him. He moved to California and worked asa computer programmer and a rock-climbing instructorand river guide, according to theTimes. At this point, Ellison said he was pretty happy with his life.

But after a series of jobs, he became part of a company working to establish a new type of software database. That company would become Oracle, now one of the largest software companies in the world.

Ellison, like other titans on this list, is interested in extending human lifespan, andhas given over $330 million for researchinto aging and related diseases.

Four-times divorced, Ellison has two adult children and calls his $70 million Woodside, Calif. estate home. However, Ellisonsmassive real estate portfoliomeans he never spends much time in one place. He owns additional properties in Japan, San Francisco, Malibu, Lake Tahoe and Rhode Island.

Brin, 44, also made his fortune in the tech industry as one of the storied co-founders of Google, along with Larry Page (No. 5). Born in the Soviet Union, Brin and his family, who is Jewish, came to the U.S.when Brin was just six-years-old after facing anti-Semitismin their home country.

At Google, the entrepreneur headed up Google X, a secretive division of the company, until becoming president of Googles new parent company, Alphabet, in 2015. While running the Google X labs, he was rumored to bebuilding a secret airship in a massive airplane hangarin Silicon Valley.

Brin has donated around$50 million to Parkinson researchafter discovering he has a genetic mutation predisposing him to the disease. He alsogave $1 million to the Hebrew Immigrant Aid Society, the organization that helped him leave Russia as a child.

The Koch brothersCharles, 82, and David Koch, 77tie for eighth place as two of the richest people in America.

Charles isthe chairman and CEO of Koch Industries, a Kansas-based conglomerate with $100 billion in annual revenue. David isthe vice president of the company, and both own 42% of the company.

The men both graduated from MIT with degrees in engineering and joined their familys business upon graduating, according toBloomberg.

In 1976, Charles established a libertarian think tank called the Cato Institute, which the brothers latersued over a debate about ownership rights.

The Koch brothers are politically active,having donated hundreds of millions of dollarsto Republican and conservative causes in their lifetimes.

(MONEYs parent company, Time Inc., is in the process of being acquired by Meredith Corporation in a deal financially backed by the private equity arm of Koch Industries.)

Walton, 73, is the eldest son of Walmart founder Sam Walton and the former chairman of the company. He stepped down from his role in 2015 after running the chain for 23 years, though he still sits on its board.

The majority of Waltons wealth comes from his shares in the company, andBloombergestimates he owns about 13% of the family business.

Before going to work for his father at the worlds largest retailer, Walton played football at the University of Arkansas andgraduated from Columbia Law School.

Heowns multiple properties including a home in Aspen, Colo. and another Paradise Valley, Ariz., and recently purchased 1,500 acres of land in Hawaii, reportedly to build a resort.

Walton currently lives inBentonville, Arkansas, and is marriedwith three children.

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