Denver, Colorado may have the biggest head start for marijuana as an industry. The Colorado capital has been recreational-weed friendly since 2012.
Venice Beach in Los Angeles was one of the first places activists started to call for the legalization of marijuana in the 1980s.
Colorado authorities had to replace the 420-mile marker near the state's border with Kansas after it kept disappearing. The current marker reads 419.99.
Bob Dylan is said to have introduced the Beatles to marijuana at the former Delmonico Hotel in New York City, now Trump Park Avenue.
Portland, Oregon is a marijuana hotbed thanks to its legal recreational weed status.
The Haight-Ashbury neighborhood of San Francisco has long been associated with the Summer of Love and drug culture. Here, revelers celebrate a 4/20 event on nearby Hippie Hill, located in Golden Gate Park.
Seattle hosts its Hempfest every August, attracting thousands of smokers as well as speakers and legalization advocates.