LOS ANGELES — In California on New Year’s Day, retail marijuana sales will be legal­ for the first time — more than two decades after the state paved the way for legalization by passing the nation’s first medical marijuana law.

Other states, though, were quicker to allow recreational use of pot.

The first of about six dozen shops licensed by the state will open Monday.

Twenty-eight other states have adopted similar laws. In 2012, Colorado and Washington became the first states to legalize recreational marijuana. California is one of five states, plus Washington, D.C., that followed suit. Retail sales are scheduled to begin in July in Massachusetts.

In California, it’s legal for adults 21 and older to grow six plants and possess an ounce of marijuana.

‘‘We’re thrilled,’’ said Khalil Moutawakkil, founder of KindPeoples, which grows and sells marijuana in Santa Cruz. ‘‘We can talk about the good, the bad and the ugly of the specific regulations, but at the end of the day it’s a giant step forward, and we’ll have to work out the kinks as we go.’’

California banned ‘‘loco-weed’’ in 1913, according to a history by the National Organization for the Reform of Marijuana Laws. The first attempt to undo that by voter initiative failed, in 1972; three years later felony possession of less than an ounce was downgraded to a misdemeanor.

In 1996, voters approved marijuana for medicinal purposes. ‘‘The heavens didn’t fall,’’ said Dale Gieringer, director of California NORML.

Associated Press