Even before Canada moved to legalize recreational cannabis use in October, it was clear to many investors that the legal marijuana industry was one to watch out for. Ten states in the United States have legalized recreational marijuana, while 30 have approved medicinal marijuana use in one form or another.

Now that the legal cannabis industry has roots in the U.S. and Canada, companies are clamoring to get on top. A recent report from the Motley Fool suggests that as much as $5 billion in annual sales can be expected once the industry is fully grown. Beyond that, with the U.S. Food and Drug Administration (FDA) having approved its first cannabis-based drug in June of this year, things are looking up for marijuana stocks.

At the moment, there are more companies in the marijuana industry than there are marijuana stocks available on U.S. exchanges. As time goes on, however, investors should keep their eyes on the growing list of marijuana companies on top exchanges. Below, we catalog a few of the marijuana firms that investors may see on U.S. exchanges in the near future.

OrganiGram Holdings

So far this year, fewer than half a dozen marijuana stocks have made the shift from over-the-counter (OTC) exchanges to reputable exchanges like the Nasdaq or the NYSE. OrganiGram Holdings (OGRMF) may be one of the next companies to swim upstream.

OrganiGram has a market cap of around $600 million, making it a suitable choice for listing on the Nasdaq exchange or potentially even the NYSE. What's more, the marijuana production company only has plans to ramp up operations. When it's finally to-scale, the Motley Fool reports that OrganiGram will likely be one of the 10 largest cannabis producers in Canada. But getting to this point could take time. The company only recently announced its plans to up production in New Brunswick, with a timeline of a year and a half.

Importantly, OrganiGram has achieved a rare prize among marijuana companies: it has been able to eke out a quarterly profit. Investors should take note of the early success of this firm, particularly if it ends up listing on a major exchange.

Auxly Cannabis Group

Although it trades in OTC exchanges for less than $1 per share, Auxly Cannabis Group (CBWTF) has a market cap of more than $500 million. That's due in large part to massive changes the company has seen in recent quarters. Auxly has aimed to take on royalty business in the downstream, midstream, and upstream areas of the cannabis growing business. With a broad range of partners across the industry, Auxly is positioned to become one of the 10 largest retailers in the future.

Auxly may be a bit of a long shot for uplisting, though, as the company operates exclusively in Canada. That means that the company would only list on exchanges in the U.S. if it expanded to the U.S. market. Whether or not Auxly will expand internationally remains to be seen.

CannTrust Holdings

With rapidly-expanding growth operations across Canada, CannTrust Holdings (CNTTF) is another growing operation and a likely candidate for exchange listing. CannTrust is developing a one-million-square-foot hydroponic farm in order to produce marijuana products with the lowest possible cost and highest margins. The company has seen particular success with its cannabis oil sales and boasts a market cap of around $750 million. With the marijuana industry, nothing is sure, but investors should watch out for news of CannTrust's continued expansion, including its potential to be listed on mainstream U.S. exchanges.