This April 20th aka "4-20" in Boulder there was one of the largest collections of marijuana legalization supporters ever. Here's a picture of CU that day.

You could smell the weed in the air, several blocks away from this scene. Snarfs, the sandwich shop where I work, doubled and nearly tripled it's normal daily sales. Ahh, the munchies.
Within the past year, medical marijuana has been legalized here, and so there are dispensaries on many corners and lots of people have figured out a way to get a medical card for the drug. I don't smoke, but am loosely in favor of legalization of marijuana, though I don't agree with its legalization being solely through the 'medical' pathways. So many people are clearly blurring that distinction and using it for recreational purposes under the guise of 'pain relief'.
In any case, this whole April, here, has been full of various cannibis-related events. And I particularly loved the above peacock poster.