These are the 21 richest American entrepreneurs under 40 — and they all made their fortunes in tech

Forbes has released its first ever list of the richest American entrepreneurs under 40 years old, and it's completely dominated by the tech industry in California. 

Of the 40 entrepreneurs they looked at, a full 34 made their money in tech, with 33 living in California. They included those who were either born in the US or who built their companies here.

When we narrowed the focus to only those who had made over $1 billion, the list dropped to 21, and every single one had made their fortune in tech.

These mostly self-made billionaires include founders of some of the most iconic tech companies of the past few years, like Airbnb, Facebook, Twitter, and Uber. 

Here are the 21 youngest billionaires in the country, who prove that tech is now ground zero for the American Dream.

Additional reporting by Tess Danielson and Tanza Loudenback.

21. Orion Hindawi

Net Worth: $1 billion

Age: 35

Orion Hindawi made his fortune through the security startup Tanium, where he is CTO. Tanium was valued at $3.5 billion after raising $120 million in September. Hindawi works with his father, David, who was one of the founders of the startup, and the two previously worked together at David's last company, BigFix, which IBM bought for a reported $400 million in 2007.

20. Evan Sharp

Net Worth: $1.05 billion

Age: 32

Evan Sharp is a cofounder of Pinterest, which he helped start as a side project with friends while at architecture school back in 2009. What started as a fun project has now boomed into a site with 47.66 million unique monthly visitors in the US, and which is now valued at $11 billion.

19. Brian Sheth

Brian Sheth showing off Vista Equity's snazzy fashion sense at #Buyouts Texas pic.twitter.com/ya4TIKxJte

— Luisa Beltran (@LuisaRBeltran) December 10, 2013

Net Worth: $1.1 billion

Age: 39

Sheth is cofounder and president of Vista Equity, the technology-focused private equity firm founded in 2000. He is actively involved in his company’s investments and sits on 16 separate boards of businesses funded by Vista Equity. Sheth additionally serves as a director at Waterfall Mobile, MarVista Entertainment, and Global Wildlife Conservation.