If you're an investor, there's a good chance you've been unable to avoid the discussion of "marijuana stocks" in recent years. And there's a good reason for that: growth.

According to cannabis research firm ArcView, North American legal weed sales soared 33% in 2017 to $9.7 billion, and they're expected to grow by a robust compound annual rate of 28% through 2021. Should this forecast come to fruition, the North American legal pot industry could be generating nearly $25 billion in annual sales by the end of 2021.

But what you may not realize is just how much history the legal marijuana industry has made this year, even as we have five months to go before we turn the page on 2018. In no particular order, here are nine "marijuana firsts" for 2018.

Trimmed cannabis buds next to a piece of paper that says yes, lying on dozens of miniature Canadian flags.

Image source: Getty Images.

1. Canada gives the green light to recreational pot

Without a doubt, the most exciting development this year has been the passage of the Cannabis Act (officially bill C-45) in Canada on June 19. Following months of debate, and nearly two weeks of back-and-forth between the House of Commons and the Senate, the Cannabis Act was easily passed, which clears the way for recreational marijuana to be sold, as of Oct. 17. No other industrialized country in the world has given the green light to adult-use pot.

Though estimates vary, this legalization could generate an additional $5 billion a year for the industry, atop what it's already bringing in via domestic medical sales and exports.

2. Vermont OKs recreational cannabis through the legislative process

In the U.S., one of the biggest stories occurred in January, when Vermont became the ninth state to OK the adult-use of marijuana. (However, the state doesn't allow for the drug to be purchased in dispensaries.)

What's particularly unique about Vermont's recreational approval is that it's the first to be done entirely through the legislative process. Vermont is one of two dozen states that doesn't have the initiative and referendum process, which means that all legislation has to be proposed and approved within the confines of the state's legislature. In essence, residents don't vote on legal issues within the state, making this approval that much more special.

Cannabis leaves next to test tubes and other biotech lab equipment.

Image source: GW Pharmaceuticals.

3. The first cannabis-derived drug wins FDA approval

More recently, on June 25, the U.S. Food and Drug Administration (FDA) approved GW Pharmaceuticals' (NASDAQ:GWPH) Epidiolex, a cannabidiol (CBD)-based oral medicine designed to treat two rare types of childhood-onset epilepsy known as Dravet syndrome and Lennox-Gastaut syndrome. In multiple pivotal-stage studies, GW Pharmaceuticals' lead drug easily met its primary endpoint by demonstrating a statistically significant reduction in seizure frequency relative to baseline and the placebo.

But the bigger news is that GW Pharmaceuticals' Epidiolex became the first cannabis-derived therapy to get an FDA thumbs-up. Since marijuana remains a Schedule I drug at the federal level in the U.S., and Schedule I substances are deemed to have no recognized medical benefits, a cannabis conundrum has been created in Washington.

4. Aurora Cannabis completes the largest marijuana buyout in history

We've also seen the largest pot stock deal in history come to fruition. Earlier this year, Aurora Cannabis (NYSE:ACB) acquired Saskatchewan-based CanniMed Therapeutics for $852 million. Then, just over a week ago, it clobbered that record by completing its all-share purchase of Ontario-based MedReleaf for approximately $2.5 billion.

Why so aggressive on the capacity expansion front? The simple reason is that Aurora Cannabis is looking to secure long-term supply deals and ample market share. However, it should be noted that Aurora Cannabis is primarily focused on the medical market, meaning its top-tier production -- an estimated 570,000 kilograms a year, when at fully capacity -- will mostly find its way to overseas markets.

A television studio with the Nasdaq digital tickerboard in the background.

Image source: Nasdaq.

5. Cronos Group becomes the first pot stock to uplist to a major exchange

Ontario-based Cronos Group (NASDAQ:CRON), of all growers, made history in late February by becoming the first marijuana stock to uplist from the over-the-counter (OTC) exchange to a reputable exchange in the United States, the Nasdaq.

Uplisting to the Nasdaq provides two perceived benefits for Cronos Group, and pot stocks that may follow in its footsteps. First, it adds improved liquidity and validity to the legal marijuana industry, which may encourage investors to buy in. And second, it makes Cronos Group more appealing to financial institutions, many of which won't invest in companies that are listed on the OTC exchange.

6. Canopy Growth is the first to join the NYSE

Interestingly enough, Canopy Growth Corporation (NYSE:CGC), the largest marijuana stock by market cap, was on track to become the first marijuana stock to uplist from the OTC exchange last year. But this move was derailed by a roughly $190 million investment (a 9.9% equity stake) from Corona-beer owner Constellation Brands in late October.

However, that didn't stop Canopy Growth from becoming the first marijuana stock to uplist to the prestigious New York Stock Exchange in May. Like Cronos Group, listing on a more reputable exchange should improve liquidity, validity, and perhaps even access to capital.

A tipped over jar filled with trimmed cannabis, next to a clear scoop with a cannabis bud inside.

Image source: Getty Images.

7. MedMen Enterprises becomes the largest U.S. pot stock to head north

Posh cannabis retailer MedMen Enterprises (NASDAQOTH:MMNFF) made history of its own in May by becoming the largest U.S.-based company to seek to list its shares publicly in Canada through a reverse merger. Initially, shares of the upscale dispensary chain, which currently has 13 stores (and three in development) in three U.S. states, commanded a $1.7 billion valuation following its debut.

Why list in Canada? The simple answer is that the legalization of recreational marijuana has made the environment considerably more conducive to investment. Within the U.S., as noted, marijuana remains a Schedule I drug at the federal level, which could curb investment appeal in MedMen's stock.

8. Tilray makes history with its Nasdaq IPO

Of course, we've also seen the opposite of what MedMen did: Canadian-based Tilray (NASDAQ:TLRY) became the largest Canadian pot stock in history to go the initial public offering (IPO) route on a reputable U.S. exchange, the Nasdaq. Following Tilray's July IPO, its valuation briefly spiked to north of $2 billion.

As with the other pot stocks mentioned, Tilray aims to improve liquidity and validity by listing on a reputable U.S. exchange. It will also now have much easier access to capital via common-stock issuances, convertible debt raises, and even access to basic banking services now that recreational pot will be legal in our neighbor to the north. Expect Tilray to use the $153 million in gross proceeds from its IPO to further its capacity expansion.

A cannabis leaf lying atop a hundred dollar bill, with Ben Franklin's eyes poking through the leaves.

Image source: Getty Images.

9. Bank of Montreal co-led a round of cannabis equity financing

Last, but not least, we saw marijuana history when Bank of Montreal (NYSE:BMO) co-led a round of equity financing for Canopy Growth in February. The equity offering, which was valued at around $136 million at the time and was co-led with GMP Securities, was the first in which a major Canadian bank was involved.

Understandably, the dynamics of equity financing have changed since the Cannabis Act was passed on June 19. It's now perfectly kosher for Canadian financial institutions to offer basic banking services to domestic marijuana companies, and they should be eager to do so with big dollar signs being tossed around in the post-legalization environment. But in terms of breaking the mold, that belongs to Bank of Montreal.

Sean Williams has no position in any of the stocks mentioned. The Motley Fool recommends Nasdaq. The Motley Fool has a disclosure policy.