An open gate in the Mississippi flood wall south of downtown. This is the graffiti-permitted stretch. You see these "free the herb" tags everywhere around the city, always with the same lettering. The tagger may be stoned but he or she is persistent.
However, I don't think it will ever be legalized in this state. We have an increasingly hard right government with a few islands of progressives scattered across. If you want it easy and legal, drive out to Colorado.
By the way, the old factory in the background is across the river in Illinois.