Oregon and Colorado also have marijuana legalization on their ballots – but polls show Washington is the most likely to say yes. Nineteen states have already legalized the medical use of marijuana.
Initiative 502 would legalize possession of up to one ounce of marijuana for anyone over 21. Farmers would be issued state licences to grow it and, their product would be sold in stand-alone stores.
Supporters say it could generate nearly $2 billion US in tax revenue over the next five years that would be earmarked for healthcare, drug treatment and education.
But that is only if the federal government doesn't try to block the law from taking effect, since pot remains illegal under U.S. federal law.
Initiative 502 also remains controversial even amongst marijuana advocates in the state because it says cannabis would remain a controlled substance under U.S. law and possession or growing of unlicensed cannabis would still be illegal.
Catching the buzz in B.C.
Marijuana advocates in B.C. are watching the Washington referendum closely. Long-time pro-marijuana campaigner and former B.C. NDP leadership candidate Dana Larsen says if the intiative passes, it would help his campaign to have marijuana decriminalized in B.C.
"There's a common argument against cannabis reform in Canada, that America will freak out in some way, or shut down the border, or there will be some kind of problems," said Larsen.
"When our neighbour to the south legalizes marijuana in their state, it's really going to put the light out of the argument and show that we have the power in Canada to do as we choose as well."
The latest public opinion poll showed 75 per cent of British Columbians favour taxing and regulating marijuana instead of chasing growers and sellers.
"I think it will inspire people here to see that if they can do it in Washington and have a referendum on cannabis law, then we can do it here in British Columbia as well."Suggest a correction