Climbing stock markets and rising real estate values helped create nearly 500,000 new millionaires in the U.S. in 2014, according to a new report. The study, from market research and consulting firm Spectrem Group, found that there are now 10.1 million households in the U.S. with $1 million or more in investable assets, excluding the value of their primary residence. That's up from about 9.6 million in 2013, and tops the prerecession peak of 9.2 million in 2007. It's the highest number since Spectrem began tracking the data in 1997.

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The number of households worth $5 million or more also set a new record, jumping to 1.3 million from 1.24 million in 2013. And there are now 142,000 households worth $25 million or more, up from 132,000 in 2013. Read MoreWhere millionaires are moving—and fleeing—around the world

While the rich are indeed getting richer, what's most notable is that more people are becoming wealthy. Since the millionaire population plunged in 2008, the U.S. has gained or added back more than 3.5 million millionaires. The result? There are now more than twice as many millionaire households than there were in 1996. "The number of wealthy households is at the highest level to date," said George H. Walper Jr., president of Spectrem Group. "Given the record levels in the financial markets in 2014, a significant recovery in real estate and investors' perceptions of the increased value of their privately held business, it is not surprising that we see these record levels."