According to online results from the Denver Elections Division, 89,320 people voted in favor of decriminalizing, while 87,341 others voted against it. Election officials said on Twitter that the "results remain unofficial" until they are certified on May 16.
The initiative on the ballot followed the same tack taken by marijuana activists to decriminalize pot possession in 2005 in the city.
Psychedelic mushrooms, also known as " magic mushrooms" is a hallucinogenic chemical obtained from certain types of fresh and dried mushrooms.
A number of other states have since allowed marijuana sales and use by adults.
What De Ligt Said To Man United About Summer Transfer
If he did, he would follow in the footsteps of team-mate Frenkie de Jong , who will join Ernesto Valverde's side in the summer. De Ligt is claimed to prefer the opportunity of moving to La Liga, with Barca believed to be favourites to land his signature.
Kevin Matthews, director of the Decriminalize Denver campaign, said psilocybin has helped him deal with depression for years.
The vote referred specifically to psilocybin, the psychedelic chemical in magic mushrooms which under USA federal law belongs to the same group of banned drugs as heroin and LSD.
The language of Initiative 301 prohibits "the city from spending resources to impose criminal penalties" for personal use, possession and growth of mushrooms.
The federal government classifies psilocybin as a Schedule I drug, with no medical goal and a high potential for abuse.
"Humans have used these mushrooms for thousands of years for healing, rites of passage, spiritual insight", said the organisation Decriminalize Denver, which in January announced it had collected enough signatures to put the measure to a vote.
Before the vote Denver's district attorney Beth McCann said that, although she was against the motion, if it passed she would support the formation of a review panel to study the effects of the drug. But a growing body of medical research shows that psilocybin can treat conditions like anxiety and depression, in cases where drugs now on the market cannot. "One arrest is too many for something with such low and manageable risks for most people, relative to its potential benefits".