Oakland International Airport could become home to the USA's first legal marijuana growing factory under plans drawn up by California-based Gropech.

The 60,000sqft cannabis 'superstore', would house up to 30,000 marijuana plants and produce an estimated 20,000lbs of the drug for medicinal purposes a year.

The factory, which is expected to open in January 2011, will generate an estimated $5 million in tax revenue for Oakland each year and employ some 200 people.

Gropech is hoping to apply for one of four Oakland government permits, expected to be issued next year, to build large-scale medical cannabis farms within city limits.

Oakland mayoral candidate Don Perata, Jean Quan and Oakland Council member Larry Reid, along with hundreds of other visitors attended the official unveiling of the proposed plans and the  of the weGrow as a national enterprise.

"We have four medical centers in Oakland, So, we are a natural for having an industry sprout up," Perata told the abc's KGO San Francisico TV station.

The announcement comes a month before Californians go to the polls for a historic referendum to decide whether to make recreational marijuana use legal within the state.

By Oliver Clark