The U.S. cannabis space is blooming.

With 33 states now offering some form of legal medical or recreational marijuana, and pot companies expanding their footprints across the country, the cannabis "gold rush" is underway — and it won't stop anytime soon, says Ben Kovler, founder, chairman and CEO of multistate operator Green Thumb Industries.

"The opportunity in cannabis is here in the U.S.," Kovler said Wednesday on CNBC's "Fast Money," adding that "the phone rings a lot" at Green Thumb as companies in diverse sectors start to field opportunities in the space.

"This is where the market is," he said. "This is a $50 [billion] to $80 billion industry where total market capitalization is still under $15 billion. So it's a really exciting time, and you can see that the U.S. is where the operators want to be."

And, with industry leader Canopy Growth in talks to acquire multistate operator Acreage Holdings, Kovler's point is being made for him. Shares of both companies surged in after-hours trading Wednesday.

To Kovler, who is also an heir to the Jim Beam Bourbon fortune courtesy of a distant relative, the broader market's reaction will be "another step along the way of the U.S. investor starting to understand that the opportunity is in U.S. [multistate operators] that are listed in Canada," he said. "And so, I think you see continued interest in the space."

Why U.S. cannabis? If you ask Kovler, who founded Green Thumb Industries five years ago to operate in limited-license U.S. markets that now include Nevada, Ohio and Connecticut, there are two under-the-radar factors driving the boom.

"Fundamentally, in the U.S., cannabis stands at the cross-section of the opioid epidemic that is killing people — cannabis offers relief for that — and U.S. states that are bankrupt and need revenue," he said. "And cannabis is an opportunity for monstrous tax revenue."

And, while tax revenue growth in the nation's oldest and largest market, California, started off slowly, Kovler said the Golden State is an "anomaly" when it comes to this gold rush.

"If you look at Nevada, with over $100 million, Colorado with over $100 million, and you're about to see what's going to happen in Massachusetts as Adult-Use Tax and Regulate takes over, the dollars are very real," the CEO said. "We're able to build schools and help communities."

Green Thumb Industries went public on the Canadian Securities Exchange in June. The company now operates retail locations in Illinois, Massachusetts, Maryland, Pennsylvania, Nevada, Florida, California and Colorado, with approvals pending for Ohio, New York and New Jersey.