While most Americans were concerned with just deciding their new president, some states offered voters something extra on election day.

California voters passed a ballot measure to legalise the recreational use of marijuana, giving a big boost to the campaign to end the drug’s national prohibition.

People aged over 21 can now legally possess up to an ounce of marijuana and grow six plants.

California was one of five states where votes were considering the legalisation of recreational marijuana on Tuesday. Four other states were considering measures to legalise medicinal marijuana.

Current projections expect Nevada, Arizona, Massachusetts and Maine to pass measures to legalise the plant.

Collectively, it’s the closest the US has ever come to national referendum on marijuana.

In October, public support to legalise cannabis use was favoured by 60 per cent of the US population – its highest level is 47 years, according to Gallup.

However, The Drug Enforcement Administration has long classified cannabis as a Schedule I controlled substance, the most restrictive classification.

As of August, the DEA rejected an appeal to stop classifying cannabis as a Schedule I drug.

By Thursday, nine states could legalise recreational marijuana. Photo: Getty

North Dakota, Montana, Arkansas and Florida also joined the push and are all expected to approve cannabis for medical use.

Colorado and Washington became the first states to legalise recreational marijuana in 2012, paving the way for Oregon and Alaska to follow suit.

California is expected to have a recreational marijuana market greater than all four states combined.

The market for both recreational and medicinal marijuana is now projected to grow to $22 billion by 2020, up from $7 billion this year, according to The New York Times.

Legal marijuana sales nationwide jumped to $5.4 billion last year, an increase from $4.6 billion in 2014, according to a study by ArcView Market Research, which produces an annual report on the cannabis industry.