The state was the first to legalize medicinal marijuana use, with voters passing it in 1996. Since then, 14 states have followed California's lead, even though marijuana remains illegal under federal law.
"This is a watershed moment in the decades-long struggle to end failed marijuana prohibition in this country," said Stephen Gutwillig, California director for the Drug Policy Alliance. "We really can't overstate the significance of Californians being the first to have the opportunity to end this public policy disaster."
California is not alone in the push to expand legal use of marijuana. Legislators in Rhode Island, another state hit hard by the economic downturn, are considering a plan to decriminalize possession of an ounce or less by anyone 18 or older.
High Anxiety: Pot Growers Fear Legal Weed
A proposal to legalize the sale and use of marijuana in Washington was recently defeated in that state's legislature, though lawmakers there did expand the pool of medical professionals that could prescribe the drug for medicinal use.
And a group in Nevada is pushing an initiative that marks the state's fourth attempt in a decade to legalize the drug.
The California secretary of state's office certified the initiative for the general election ballot Wednesday after it was determined that supporters had gathered enough valid signatures.
The initiative would allow those 21 years and older to possess up to one ounce of marijuana, enough to roll dozens of marijuana cigarettes. Residents also could grow their own crop of the plant in gardens measuring up to 25 square feet.
The proposal would ban users from ingesting marijuana in public or smoking it while minors are present. It also would make it illegal to possess the drug on school grounds or drive while under its influence.
Local governments would decide whether to permit and tax marijuana sales.
Proponents of the measure say legalizing marijuana could save the state $200 million a year by reducing public safety costs. At the same time, it could generate tax revenue for local governments.
A Field Poll taken in April found a slim majority of California voters supported legalizing and taxing marijuana to help bridge the state budget deficit.
Those who grow and sell it illegally fear legalization would drive down the price and force them to compete against corporate marijuana cultivators.
Other opponents view marijuana as a "gateway drug" that, when used by young people, could lead them to try other, harder drugs. They worry that legalization would persuade more people to try it, worsening the nation's drug culture.
"We are quite concerned that by legalizing marijuana, it will definitely lower the perception of risk, and we will see youth use go through the roof," said Aimee Hendle, a spokeswoman for Californians for Drug Free Youth.
The initiative is the second proposal to qualify for the November ballot. The other is an $11.1 billion water bond measure championed by Gov. Arnold Schwarzenegger and the state Legislature.