Elon Musk's ascent to become the world's first trillionaire has revived interest in a question that once captivated an earlier generation: who was the first billionaire and, before that, the first millionaire?
Musk crossed the trillion-dollar threshold on Friday after a record-setting initial public offering by SpaceX, his rocket and artificial intelligence company. The company ended the day with a valuation of more than $2 trillion, pushing Musk's net worth to an estimated $1.2 trillion.
The achievement generated headlines around the world and sparked debate over wealth inequality, much as earlier milestones in the history of personal fortunes did.
New York City Mayor Zohran Mamdani reacted to the news on social media, writing: "Reason #1,000,000,000,000 why we should tax the rich."
Senator Elizabeth Warren also weighed in, saying the average US household would have to work for more than 11 million years to accumulate Musk's level of wealth, according to The New York Times.
While the idea of a trillionaire may seem unprecedented, historians note that similar fascination surrounded the emergence of the world's first billionaire more than a century ago.
According to The New York Times, that distinction belongs to John D. Rockefeller, the American oil magnate and founder of Standard Oil. Rockefeller became a billionaire on September 29, 1916, making him the first billionaire in the United States and almost certainly the first in the world.
Christopher McKnight Nichols, a history professor at Ohio State University who studies the Gilded Age, told The New York Times that Rockefeller's milestone was widely discussed at the time.
"People really were thinking in the way that we do now as contemporaries about, 'Oh wow, now he'll have twice as much as the next highest person on the list,'" Nichols told The New York Times.
A billion dollars in 1916 would be worth more than $30 billion today, according to the report. Rockefeller's fortune crossed the threshold after a surge in Standard Oil stock pushed share prices above $2,000.
Nichols said many Americans at the time struggled to comprehend what being a billionaire actually meant.
"I think a billionaire then is like a trillionaire now," Professor Nichols told The New York Times. "You simply can't fathom that many zeros."
The report notes that Rockefeller's rise occurred during the Progressive Era, when public concern about concentrated wealth was growing and the federal government was attempting to curb the power of industrial monopolies. Ironically, Rockefeller's wealth increased significantly after the 1911 breakup of Standard Oil into dozens of smaller companies, which later became highly valuable.
Before Rockefeller, the title of America's first millionaire is generally attributed to John Jacob Astor, a businessman who built a vast fortune through real estate investments in New York City.
According to Nichols, quoted by The New York Times, Astor most likely became a millionaire sometime during the 1820s. By the time of his death in 1848, he was worth tens of millions of dollars.
Unlike Rockefeller or Musk, Astor's wealth attracted far less public attention. The concentration of wealth was not a major political issue during his era, and most ordinary Americans would have known little about the extent of his fortune, the report said.
Looking ahead, Nichols believes Musk may not remain the world's only trillionaire for long.
"I would suspect in the very near term we will see, through AI IPOs, another trillionaire," he told The New York Times.
The comparison between Astor, Rockefeller and Musk highlights how each era has produced fortunes that seemed almost unimaginable at the time. What was once a million dollars, then a billion dollars, has now become a trillion-dollar benchmark, reflecting both economic growth and the extraordinary concentration of wealth in successive generations.
