For many years, marijuana stocks were the hottest thing on Wall Street. Early investors in brand-name pot stocks managed to generate gains of 1,000%, 3,000%, and even more than 7,000% in some instances in just a few years. But as is true of all next-big-thing industries over the past quarter of a century, all good things come to an end.

The past six months have been nothing short of brutal for cannabis stock investors. The Horizons Marijuana Life Sciences ETF, the first exchange-traded fund focused on cannabis, has shed nearly half of its value.

And if that wasn't enough to demonstrate just how poor things have gone for pot stocks, here's another statistic to chew on: At the industry's peak, there were 17 pot stocks with a billion-dollar valuation. Today, there are only nine left with a market cap in excess of $1 billion. Harvest Health & Recreation, HEXO, OrganiGram, CannTrust, Cresco Labs, Trulieve Cannabis, Acreage Holdings, and Charlotte's Web all once sported billion-dollar market caps, but do no longer.

Here's a brief look at the nine pot stocks with hefty market caps that remain.

A handful of dried cannabis buds lying atop a messy pile of cash.

Image source: Getty Images.

1. Canopy Growth: $7.63 billion

As has been the case for quite some time, Canopy Growth (NYSE:CGC) remains the largest marijuana stock in the world by market cap. However, it's a tough pill to swallow considering that its market cap used to be more like $17 billion. While Canopy Growth still projects as the second-biggest cannabis producer in Canada and has a mammoth international presence, the company is also operating without a permanent CEO, has been losing copious amounts of money in recent quarters, and has been stymied with persistent supply issues throughout Canada. The way things appear now, Canopy Growth may be one of the last marijuana growers to turn a profit.

2. Aurora Cannabis: $4.2 billion

Things aren't much better for Aurora Cannabis (NYSE:ACB), which was once a nearly $10 billion company. Aurora actually one-ups Canopy Growth in both the peak production and international reach departments. However, the company's aggressive acquisition strategy has led to a mountain of goodwill being carried around on its balance sheet. At 3.17 billion Canadian dollars, goodwill accounts for 58% of Aurora's total assets, making it potentially susceptible to a massive writedown. Add in the fact that Aurora's overseas markets are unlikely to generate significant sales for the company until domestic market demand is met, and you have a recipe for big declines.

3. GW Pharmaceuticals: $3.32 billion

Cannabinoid-based drug developer GW Pharmaceuticals (NASDAQ:GWPH) may not want to be called a marijuana stock, but it's certainly being treated like one at the moment. Once valued at nearly $6 billion, the drugmaker with the only Food and Drug Administration (FDA)-approved cannabis-derived drug (Epidiolex) has hit hard times. Though GW Pharmaceuticals' lead drug has launched strongly out of the gate as a treatment for two rare forms of childhood-onset epilepsy, an aggressive forward valuation, along with tempered expectations from GW's stock on Wall Street, has deflated this promising biotech company.

A vape pen next to a vial of liquid and neatly arranged dried cannabis flower.

Image source: Getty Images.

4. Cronos Group: $2.99 billion

Another instance of "how the mighty have fallen" belongs to Cronos Group (NASDAQ:CRON). Cronos was riding high in the first quarter after netting a $1.8 billion equity investment from Altria Group, thereby resolving any near-term liquidity concerns. Unfortunately, Cronos has been slow to develop the assets it does have, and it's clearly been hurt by supply issues throughout Canada. Making matters worse, the company is now exposed to a flurry of vape-related health concerns stemming from the United States. Down more than $4 billion in market cap from its peak, Cronos Group has its shareholders in a world of hurt.

5. Curaleaf Holdings: $2.88 billion

Despite recent weakness, U.S. vertically integrated multistate operator Curaleaf Holdings (OTC:CURLF) now finds itself as a top five cannabis stock. Though Curaleaf has had issues to contend with, including an FDA warning letter for its topical cannabidiol products, the company's pending acquisitions of Cura Partners for $949 million and Grassroots for about $875 million should give it a real shot to hit $1 billion in annual sales in 2020. When these deals close, Curaleaf will have nearly 70 operational retail locations, which is far and away more than any other multistate operator, as well as 131 retail licenses in 19 states. Suffice it to say that its valuation looks well deserved.

6. Tilray: $2.35 billion

Perhaps the wildest ride of all belongs to Canadian grower Tilray (NASDAQ:TLRY), which had its initial public offering in July 2018. Just two months after its list price of $17, Tilray's stock moon-shot to $300 on an intraday basis, representing a market cap of $26 billion. Today its market cap has been cut to less than a tenth of its intraday peak. While Tilray does have a well-known medical cannabis brand, and the company should have ample overseas opportunities in the years to come, its production has underwhelmed. Without sufficient dried and derivative output, Tilray has regularly turned to wholesale purchases, thereby crushing its gross margin. Like Canopy Growth, it's unclear when Tilray will be profitable, but it's pretty obvious it won't be anytime soon.

Two miniature shopping carts, one of which is holding a cannabis flower, while the other holds vials of cannabis oil.

Image source: Getty Images.

7. Green Thumb Industries: $1.85 billion

Once we move to multistate operator Green Thumb Industries (OTC:GTBIF), we're officially out of the mid-cap realm and into small-cap territory. Although it's lost nearly half of its value since the end of March, Green Thumb is giving investors reasons to be excited. The recently closed acquisition of Integral Associates brings the Essence retail name into the fold and, more importantly, gives the company access to the lucrative Nevada market. Green Thumb also looks to be top five among multistate operators in terms of retail licenses held.

8. Aphria: $1.3 billion

Aphria (NYSE:APHA) once stood toe to toe with the largest pot stocks in the world, but no longer. Even with 255,000 kilos of peak annual production potential, and coming off of a better-than-expected fourth-quarter report, Aphria's stock has virtually no sustainable momentum. Much of its weakness can be traced to a short-seller report that was released last December. Even though the allegations of the report were disproven by an independent committee, conflicts of interest surrounding a recent transaction were uncovered, eventually leading longtime CEO Vic Neufeld to step down. There are clear investor trust issues with Aphria, and they've manifested in a weaker share price.

9. Innovative Industrial Properties: $1.03 billion

Finally, cannabis real estate investment trust (REIT) Innovative Industrial Properties (NYSE:IIPR) is clinging to its billion-dollar valuation by a thread. Of the nine billion-dollar pot stocks, it's the only one that's profitable on a recurring basis. That's because the REIT model is highly predictable. Innovative Industrial currently owns 31 medical cannabis growing and/or processing facilities in 12 states, all of which combine for a weighted-average remaining lease length of 15.9 years and a return on invested capital of 14.5%. In simpler terms, this REIT will have a complete payback of its invested capital in only five years.

Could more marijuana stocks disappear from this shrinking list? Only time will tell.