Image source: Brett Levin via Flickr.

Most of us know that marijuana, or cannabis, is a widely used recreational drug that's currently more illegal than legal in the U.S., and that it has a lot of support for medicinal purposes. Many of us hold strong opinions on marijuana, too -- about whether or not it should be more widely legalized. Despite all of that, though, there's much more to know about marijuana, including some surprising information.

Here are 11 interesting things to know about marijuana:

  1. About 44% of Americans have tried marijuana, according to a 2015 Gallup poll. The percentage has grown steadily since Gallup first asked the question in 1969.

  2. Fully 11% of Americans (more than 1 in 10) reported to Gallup in 2015 that they currently smoke marijuana.

  3. Support for the legalization of marijuana has been growing, with 53% of Americans in favor of it as of 2015, per a different Gallup poll. Support is stronger among younger folks than older ones, and weaker among Hispanics than among whites and African-Americans.

  4. Americans are especially likely to favor legalization of marijuana for medicinal purposes. The drug has been found useful to treat glaucoma, epilepsy, inflammatory bowel diseases, arthritis pain, multiple sclerosis pain, and chemotherapy pain and nausea. Other possible uses include curbing the growth of cancer cells and Alzheimer's disease, stimulating appetite, and treating anxiety.

  5. It's not all good news for the drug, though. Like regular tobacco, it contains carcinogens, and inhaling a lot of smoke is not good for anyone. Though it may be less addictive than other drugs, some people do become dependent on it. It can impair driving ability, too. Many studies find marijuana to be less harmful than alcohol or tobacco, but that doesn't mean it's safe.

  6. Folklore has it that Shakespeare may have smoked marijuana, and that Queen Victoria might have used it to alleviate monthly cramps. It's also reported to have been recommended as a substitute for alcohol by prohibition campaigners in the 19th century. 

  7. Legalizing marijuana could deliver significant tax revenue to governments seeking just that. In its first year after legalizing marijuana, the state of Washington collected about $70 million in taxes. For Colorado, it was $53 million -- and marijuana tax revenue is outpacing that from alcohol in the state. The Cato Institute has estimated that state governments and the federal government could save around $8.7 billion through the legalization of the drug.

  8. Growing marijuana, like growing many other crops, requires a lot of resources. According to Mother Jones magazine, California's crop requires 50% more water during its growing season than the city of San Francisco uses in a year -- some 60 million gallons. In Denver, it's estimated that less than 2% of the city's electricity usage is for growing marijuana -- but that rate is growing rapidly.

  9. The marijuana industry in the U.S. was recently estimated to be worth about $3.5 billion, with California research company ArcView seeing that growing to $4.4 billion this year.

  10. Growing marijuana can be surprisingly profitable, with a 2015 Bloomberg report noting that while the wholesale rate for medical marijuana was $2,500 per pound, it was costing a Colorado grower just $600 to produce the stuff. A Forbes article posited that "Legal Cannabis is 2015's best start-up opportunity."

  11. You can make money (or lose it!) in medical marijuana without growing any yourself -- by investing in marijuana-centered companies. While there can be plenty of money for companies in growing and selling the stuff, big bucks can also be made by developing effective pharmaceutical drugs derived from it. Here are two publicly traded companies to look into: GW Pharmaceuticals (GWPH) is a biopharmaceutical company with a market value of $1.2 billion, while Insys Therapeutics (INSY) is another, with a market value of $1.8 billion. Both stocks have dropped in recent months, presenting better entry prices for long-term believers, but it's also quite reasonable to wait for this nascent industry to grow more and to see which companies emerge as profitable winners.

Marijuana and the industry around it are in the news a lot lately -- consider keeping an eye on it, not only for interesting information, but also possible investment opportunities.