Maine has joined California, Nevada and Massachusetts in backing recreational marijuana use in state-wide polls.
The votes, which took place alongside the presidential election, legalise the growth and consumption of cannabis for those over 21 years old.
Arizona rejected legalising recreational use. Florida and North Dakota legalised medicinal use.
The drug will be an option in the management of conditions including cancer, Aids and hepatitis C.
California said the taxes on the sale and farming of cannabis would support youth programmes, environmental protection and law enforcement.
In other ballot initiatives across the US on election night:
- Colorado voters approved a measure allowing assisted dying for the terminally ill through "medication that can be self-administered" - five other states have similar laws
- Nebraska reinstated the death penalty, overturning the state legislature's move last year to repeal capital punishment
- Oklahoma gave its capital punishment law constitutional protection, meaning it cannot be declared cruel and unusual punishment by state courts
- California voters rejected a proposal to make porn stars wear condoms in all their sex on-set scenes
- Arizona, Colorado and Maine voters approved a $12 (£9.60) minimum hourly wage by 2020, and Washington state raised it to $13.50 - the federal hourly minimum wage is $7.25
Legal marijuana is among the fastest growing industries in America, with some analysts suggesting sales could reach $22bn (£17.6bn) by 2020.
Opponents, however, had said the proposition opened the way for promotion of the drug on shows watched by young people, exhibiting "reckless disregard for child health and safety".
In Massachusetts, the legislation is set to take effect in December, with similar taxation measures to those in California.
California was one of the first states to legalise the drug for medicinal purposes in 1996.
On Tuesday, voters in Florida and North Dakota followed suit, making medicinal use legal in a majority of US states.
Many states used the general election as an opportunity to put a range of questions to the public on matters such as tax, the minimum wage or the death penalty.