Musk is also extending his empire underground. Born in 2016 from Musk’s exasperation with a traffic jam, the Boring Company is his proposed solution to congestion: “personalized mass transit,” via tunnels.

The company aims to build a network of high-speed tunnels near some of America’s most gridlocked cities. In 2017, Musk tweeted that he had “verbal govt approval” for a Hyperloop that would connect Washington, D.C., to New York City and could be traveled in 29 minutes.

No such project has taken shape.

The company’s biggest project to date is the 1.7-mile loop below the Las Vegas Convention Center, which has been used by more than 1.5 million passengers since it opened in 2021, according to the company’s website, “with a demonstrated peak capacity of over 4,500 passengers per hour, and over 32,000 passengers per day.”

The Boring Co. has yet to prove its theory that tunneling can solve traffic on a larger scale. Critics point out that rather than increasing mobility, the strategic relocation of cars underground would simply remove the traffic from view.

Musk is insistent, however: “It’s either traffic forever or tunnels,” he once tweeted.

All calculations of Musk’s wealth, his company stakes and their values are sourced from the Bloomberg Billionaires Index after market close on Jan 31, 2024.

Editing by Karly Domb Sadof and Kate Rabinowitz.