Colorado voters in November will decide whether limited possession of marijuana for any purpose should be legalized.

If passed, the initiative would make Colorado the only state in the nation to legalize marijuana for recreational use. On Monday, the measure became the first to qualify for the state’s November ballot when the Colorado Secretary of State’s Office announced its supporters had turned in enough valid signatures.

Mason Tvert, one of the measure’s chief proponents, said the campaign would use the next eight months to build a “broad base of support” across the state.

“Coloradans have a chance to make history this November, and we believe they are ready to do just that,” Tvert said in a statement.

The initiative — to be called Amendment 64 — did not make the ballot easily.

Proponents came up short of the required 86,105 valid signatures in their first attempt at submitting petitions. Given the chance to collect more signatures, they handed in another 14,000

. Nearly 7,000 of those were found valid, putting the initiative over the top.

The measure would legalize possession of up to 1 ounce of marijuana for those 21 and older. It also would allow for people to grow up to six marijuana plants in their home. Specially regulated stores would be allowed to sell marijuana, but communities would have the option of banning those businesses.

John Ingold: 303-954-1068 or jingold@denverpost.com