Elon Musk is working to revolutionize transportation both on Earth, through electric car maker Tesla — and in space, via rocket producer SpaceX. He owns 23% of Tesla but has pledged more than half his stake as collateral for loans; Forbes has discounted his stake to take the loans into account. The Tesla CEO stepped down as chairman in 2018, after making alleged “false statements” about a plan to take Tesla private, triggering an SEC probe. SpaceX, Musk’s rocket company, is valued at $74 billion after its latest funding round in February 2021. He grew up in South Africa, then immigrated to Canada at age 17. He landed in the U.S. as a transfer student to the University of Pennsylvania.