The term 420 is said to come from a high school that let out at 420. The minor students would gather to smoke dope. This celebration of children getting high on a daily basis may not be the reason. Likely the reason for the term 420 comes from nazi motorcycle gangs that sold drugs to pay for white supremacist activities and would wish themselves and their customers a happy 420. The date of 4/20 was marked with drug fueled parties just like the one in Denver.