Supporters of legalized marijuana announced today that they have gathered about 700,000 signatures for their initiative, virtually guaranteeing voters will see it on the November ballot.

They plan to turn in the petitions today to elections officials in some of the state's major counties, including Los Angeles. Supporters need 433,971 valid signatures to qualify the measure.

The measure’s main proponent, Richard Lee, a highly successful Oakland marijuana entrepreneur, bankrolled a professional signature-gathering effort that was bolstered by volunteers from the state’s hundreds of medical marijuana dispensaries.

“This is a historic first step toward ending cannabis prohibition,” Lee said. “I’ve always believed that cannabis should be taxed and regulated and that our current laws aren’t working.”

The initiative, known as the Regulate, Control and Tax Cannabis Act, would make it legal for anyone 21 and older to possess an ounce of marijuana and grow plants in an area no larger than 25 square feet for personal use. It would also allow cities and counties to permit marijuana to be grown and sold, and to impose taxes on marijuana production and sales.