There are 45 American families worth at least $10 billion, and the richest one is wealthier than Elon Musk, Forbes says.
The Walmart founder Sam Walton's heirs still own about 45% of the retail giant, giving them a combined net worth of $267 billion as of January 16, a new Forbes ranking of decabillionaire families shows. That figure dwarfs the Tesla and SpaceX CEO's net worth of about $202 billion.
Forbes estimates the 45 superrich families are collectively worth about $1.3 trillion, or roughly 10 times Warren Buffett's personal fortune.
The Mars family is a distant second to the Waltons, with a $117 billion fortune spread across the confectionery clan. There are plenty of other well-known families on the list, with names such as Koch, Lauder, Hearst, and Marriott.
Other household names, including Carnegie, Vanderbilt, and Getty, have dropped out of the rankings, for reasons ranging from stock-price performance and costly legal disputes to taxes on stock sales and charitable giving.
The descendants of John D. Rockefeller — the nation's richest man in his prime — barely made Forbes' list, with a $10.3 billion fortune.
Several of America's wealthiest families made their money by building the country's largest private companies. For example, the Cargill-MacMillan family is worth more than $60 billion thanks to their ownership of about 88% of Cargill, the ingredients giant.
Others still command stakes in public companies they helped build. The Dorrance family owns nearly 40% of Campbell Soup; the Brown family owns about half of Brown-Forman, the owner of Jack Daniel's; and the Pritzkers are the largest shareholders of Hyatt Hotels.
A few have cashed out, such as the Busch family, which sold its stake in Anheuser-Busch to InBev in 2008.
Moreover, the Haslam family sold its entire stake in a truck-stop chain called Pilot Travel Centers for about $13 billion to Warren Buffett's Berkshire Hathaway over the course of a few years.
The list of uber-rich families suggests the best way to build vast generational wealth is to establish a massive, lasting business; it doesn't seem to matter much whether it's kept in the family, taken private, or sold.