The Walmart heirs are worth $330 billion. Sam Walton's smart move in the 1950s is a big reason why.

• The Walton family is worth more than $330 billion, dwarfing Elon Musk's $237 billion fortune.
• They owe some of their wealth to a savvy decision by Walmart founder Sam Walton over 70 years ago.

The Walton family is worth about $330 billion, or way more than Elon Musk ($237 billion), per the Bloomberg Billionaires Index. Its members owe a chunk of their incredible wealth to a shrewd move by Walmart founder Sam Walton in the 1970s.

In 1953, when Walton's future retail empire was just a handful of stores, the entrepreneur took his father-in-law's advice and organized his business as a family partnership.

He gave 20% stakes to each of his four children — Jim, Rob, Alice, and the late John T. — while he and his wife, Helen, kept the final 20%.

Walton shared the main benefit of the structure in his autobiography, "Sam Walton: Made in America."

"The transfer of ownership was made so long ago that we didn't have to pay substantial gift or inheritance taxes on it," he wrote.

"The principle behind this is simple: the best way to reduce paying estate taxes is to give your assets away before they appreciate."

In other words, Walton passed down 80% of Walmart to his kids when it was worth next to nothing. They would have owed billions of dollars in estate taxes if they inherited his stock when he died a billionaire nearly 40 years later in 1992.

Parking the family's Walmart stock in the partnership, and deciding as a group when to cash out shares, had other advantages. It meant the Waltons treasured their fortune instead of "throwing it all over the place to live high," Walton wrote.

"It wasn't lavish or exorbitant, and that was part of the plan — to keep the family together as well as maintain a sense of balance in our standards."

It also ensured the family maintained control of Walmart, and could prevent it being dismantled and sold for parts. That was "the best protection there is against the takeover raiders," Walton wrote.

Giving the children a say in how the family's riches were deployed, when they were all under nine years of age, also taught them financial prudence.

"It was great moneywise, but there was another aspect to it: the relationship that was established among the children and with the family. It developed their sense of responsibility toward one another. You just can't beat that," Helen Walton wrote in the book.

Looking ahead

It's been more than 70 years since Walton opened his first five-and-dime store in Bentonville, Arkansas and established the family partnership.

He couldn't have imagined Walmart would go on to generate some $600 billion in net sales a year, employ 1.6 million Americans or roughly 1% of the US workforce, and become one of the world's largest companies worth about $600 billion.

Nor would he have foreseen that his three surviving children would eventually command net worths of nearly $100 billion each. But he would surely be pleased that the vast majority of their wealth still lies in their Walmart stock in the family trust.

Walton, who lived modestly for a billionaire, knew there was a risk that future generations could squander the family fortune on obscene indulgences like private islands.

"One of the real reasons I'm writing this book is so my grandchildren and great-grandchildren will read it years from now and know this: If you start any of that foolishness, I'll come back and haunt you. So don't even think about it."