Ranking second was Houston—another big energy town—with 18 percent growth in millionaires. Houston added 20,000 new millionaires, bringing the city's total to 131,000 millionaires with a total net worth of $496 billion.
Seattle and San Jose, California, both tech hubs, chalked up impressive millionaire growth as well. Seattle's millionaire population grew 16.9 percent and San Jose's increased 14.3 percent.
Read MoreManhattan income gap widest in US: Census
New York is still the nation's millionaire capital, with 894,000 millionaires, or more than 1 in 5 in the country. The city's millionaires have $3.2 trillion in wealth.
Yet the report said the geography of wealth is shifting along with the growth of energy and tech.
"A new pattern of wealth creation is emerging," the report said. "The emergence of fast-growing smaller cities indicates U.S. wealth is shifting to a broader mix of geographies and industries."
Read MoreWorld's billionaire population at record high
—By CNBC's Robert Frank