The Colorado Department of Transportation says the 420 mile markers on the state's highways were stolen so often, they had to replace them with 419.99 mile markers. Many people know that "420" represents marijuana - hence the popularity of the mile markers - but very few know why. It's not a police code, it's not the number of chemical compounds in cannabis, and it's certainly not Bob Marley's birthday. Today on the show, we try for the real story. Criminal is a proud member of Radiotopia from PRX. If you haven't already, please review us on iTunes! It's an important way to help new listeners discover the show: iTunes.com/CriminalShow. Say hello on Twitter, Facebook and Instagram. Sign up for The Accomplice. If you'd like to introduce friends or family members to podcasts, we created a How to Listen guide based on frequently asked questions. Artwork by Julienne Alexander.