Abillion dollars — or even a couple billion — doesn’t hack it anymore. With a record $2.9 billion cutoff to qualify for this year’s Forbes 400 list of richest Americans,  353 U.S. billionaires have fortunes too small to qualify, including famous faces like Facebook’s Sheryl Sandberg, Uber’s Travis Kalanick and Revlon’s Ron Perelman. Of the 122 Americans who became billionaires in the past year, only 27 made the ranking of America’s 400 richest — but many more may be on their way up.
One newly minted billionaire worth watching is 53-year-old prolific investor and entrepreneur Jenny Just. Over the past 24 years, Just has started or bought 15 companies. Her current portfolio ranges from insurance (National Flood Services) and video games (e-sports team Evil Geniuses) to options trading (Peak6 Capital Management). 
The biggest deal of her career will happen later this year, though. Her star investment, Apex Fintech Solutions—which handles back-office operations for mobile trading apps, robo-advisors and more—is slated to go public via a SPAC merger that values the company at $4.7 billion. That transaction, which made her a billionaire, boosted her net worth to $1.5 billion.         
The former options trader bought Apex nearly a decade ago, when the firm was teetering on the edge of bankruptcy. It focused on catering to fintechs and startups, providing the trading and technology behind firms like SoFi and Webull. The firm now manages 17 million customer accounts, including 1.6 million crypto trading accounts.
“I think it’s critical that women make decisions around money,” says Just, who was a single mother when she started the parent company, Peak6, in 1997.
The Stanford alumnus cofounded food delivery firm Doordash in 2013 to shuttle takeout around campus, then took it public on the New York Stock Exchange in December 2020.
The Bulgarian native sold trading software to hedge funds with fellow billionaire Baiju Bhatt, before the duo started popular online stock trading platform Robinhood in 2013.
A former stunt pilot, Isaacman started Shift4 Payments in the basement of his parents’ home in New Jersey in 1999. In September, he commanded SpaceX’s first civilian mission to orbit Earth.
He launched his hedge fund firm, D1 Capital Partners, merely three years ago. It now manages an estimated $20 billion in assets.
The former NYU math prof founded AI firm Amelia, known for its eponymous chatbot, in 1998. Its technology is now used by clients like Telefonica, BNP Paribas and Nordic Bank.
The world’s youngest self-made billionaire came up with the idea for Luminar Technologies, which makes gear for self-driving cars, at age 17. He dropped out of Stanford to start the company after receiving a $100,000 fellowship from billionaire Peter Thiel.
Ladies first! Tinder cofounder Wolfe Herd started Bumble, a dating app where men are forbidden from making the first move, in 2014. Its parent company went public in February.
His AbCellera uses an AI-powered platform to analyze natural immune systems and find antibodies that can be used to develop treatments, including drugs for infectious diseases and cancer.
She is famous from television. She is rich from makeup company KKW Beauty and undergarment business Skims, which was valued at $1.6 billion in April.
He cofounded investment giant BlackRock in 1988 as a part of private equity giant Blackstone Group. The New York-based business was later spun out and went public in 1999; it now manages nearly $9.5 trillion in assets.

I’m a deputy editor on Forbes’ wealth team, covering the world’s richest and their businesses. I help put together lists such as the Forbes 400, the World’s Billionaires

I’m a deputy editor on Forbes’ wealth team, covering the world’s richest and their businesses. I help put together lists such as the Forbes 400, the World’s Billionaires and America’s Richest Self-Made Women. Find me on Twitter @JenLWang or email me at [email protected]