Steps taken to thwart a public marijuana smoking event Friday at the University of Colorado appear to have worked . Protesters who gathered at a quad on the campus for the customary 4:20 light-up time dispersed without an apparent toke . In past years the Norlin Quad on the campus of the University of Colorado at Boulder had drawn 10,000 to 12,000 people for the event , which falls on April 20 ( 4/20 ) . Marijuana smokers traditionally wait until 4:20 in the afternoon to light up as a celebration of marijuana culture and a protest against drug policy . This year , the school closed the campus to outsiders and spread an unpleasant-smelling , fish-based fertilizer on the quad before enclosing it in yellow police tape and stationing police officers around the perimeter . Hours before the planned event , three students who crossed police lines and went onto the field were led away in plastic handcuffs . Several hundred students gathered around the quad as the time approached . A man began shouting into the crowd , becoming its de facto leader . When asked his name he replied , `` It does n't matter . '' `` Alright , it 's 4:20 who is ready to get weird ? '' he shouted . The crowd cheered . `` Who is with me ? '' he called out . Another cheer . The crowd seemed to expect him light up a joint , but instead he dashed under the police tape and ran across the quad as police gave chase on foot . None of his encouragers followed . Police ultimately nabbed him and carted him off in plastic handcuffs . Their leader gone , no one in the crowd seemed to know quite what to do . No one could be seen smoking marijuana and by the less legendary time of 4:30 the crowd had gone on their way . The number 420 has become synonymous with all things marijuana , but exactly why is less clear . Whatever the number 's origin , `` 420 '' events across the country have become opportunities to advocate the legalization of marijuana . The expansion of medical marijuana in California , Colorado and other states is making efforts to legalize marijuana more mainstream and making more people comfortable coming out and smoking pot in public , according to Chris Conrad , curator of the Oaksterdam Cannabis Museum in Oakland , California . Boulder 's is one of the biggest pro-pot rallies , and attendance had grown from year to year , according to university spokesman Bronson Hilliard . `` People fly in from around the country to participate , '' Hilliard explained . `` We do n't understand why they have to come to ( this ) campus . '' Celebs and the pot culture . Prior to the Colorado event , university police spokesman Ryan Huff said the smoke-ins have become too dangerous . `` It 's hard to keep track of that many people high on marijuana , '' he said . Why these marijuana advocates congregate each year on April 20 is a bit of a mystery steeped in the hazy lore of the American pot culture . Some have said 420 is a local police code for someone smoking marijuana . Others have said it refers to the number of active chemicals in marijuana . Another theory holds that 420 is a nod to Bob Dylan and his 1966 song `` Rainy Day Women # 12 & 35 '' which contains the lyric , `` Everybody must get stoned . '' Multiply 12 by 35 and you get 420 . Conrad said the leading theory traces the beginning of 420 to the early 1970s when a group of students at San Rafael High School in California would meet at 4:20 each afternoon to smoke marijuana . `` It ( was ) the time between when classes were over and their parents came home , '' he said . `` The number 420 signifies that somebody is smoking marijuana right now and it becomes a clarion call for others to join . '' Eatocracy : When celeb chefs get the munchies . According to Conrad , the story goes that the San Rafael teens named themselves `` the Waldos '' and would meet very day at 4:20 p.m. near a statue of Louis Pasteur to smoke joints . A website that claims to be associated with the Waldos declares them to be `` The Founding Fathers of 420 , '' although it does n't appear to be current . Attempts to reach the owners of the site were unsuccessful . No matter what the origin , the number now signifies the pro-marijuana culture : Craiglist ads for roommates , or for even so-called `` casual encounters , '' often note `` 420 Friendly . '' An episode of the animated TV show Family Guy called `` 420 '' involves a plot in which marijuana becomes legalized and 420 Magazine is devoted to marijuana culture . The 2003 California State Senate bill that became the law that established medical marijuana in the state was called SB420 . What began is a secret code word between stoners has gone mainstream . `` It 's a form of shorthand essentially . As far as being a secret code , it 's one of the least secret , '' explained Conrad with a laugh .
Arrests , foul weather dampen ` ` 420 '' enthusiasm . Crowds turned out , but no one showed up ; few crossed police lines . One man pumps up gas , enters quad alone , is driven away . Boulder 's is one of the biggest pro - pot rallies on cryptic grounds .