Rockefeller became the first billionaire over a century ago. Here's what to know about America's wealthiest today.

On Sept. 29, 1916, it was front page news that a surge in Standard Oil's stock price likely made oil tycoon John D. Rockefeller America's first billionaire.

More than a century later, the United States is home to hundreds of billionaires whose fortunes increasingly come from technology and financial markets. Together, they control a growing share of the country's wealth — approaching the percentage held by Gilded Age industrialists who built monopolies in railroads, oil and steel.

Here's what research tells us about America's billionaire class today.

American billionaires number over 900, according to researchers

There are a few different estimates of the number of American billionaires, but researchers tend to agree that the billionaire class exceeds 900 and is growing.

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