Civic leaders led by city mayor Gavin Newsom followed the direct example of Garstang - which declared itself the world's first Fairtrade town in 2001 - in a move which has thrilled Garstang Fairtraders, who can claim a stake in encouraging the decision.
Garstang Fairtrade pioneer Bruce Crowther was directly involved in the preliminary moves towards the West Coast US city's Fairtrade status several years ago.
Bruce said: "I received an e-mail from San Francisco a few years back saying 'San Francisco would like to follow in Garstang's footsteps.' Needless to say I was gobsmacked!
"Now it has actually happened it really is fantastic news. I am sure we will see cities like New York and Washington doing the same.
"And to think it all began here in our little, parochial market town in Lancashire - what a strange world we live in!"
Bruce, who works part-time for the UK Fairtrade Foundation and who has visited several European Fairtrade towns and cities, decided not to travel to California to share in the San Francisco celebrations, being content with visiting Fairtrade friends in Chester on Saturday.
Although the Fairtrade movement is strong in western Europe it is only in recent years that the movement has taken off in the USA, with several American communities establishing themselves as Fairtrade towns over the past few years.
The first to do so was Media, Pennsylvania, which has made approaches to Garstang Town Council for a twin town link, though formal negotiations have yet to be concluded.
With San Francisco's decision to become a Fairtrade City on World Fair Trade Day on Saturday, it now means there are two Fairtrade cities in the USA (the other is Milwaukee) and five other, smaller, Fairtrade communities.
* To become a Fairtrade community, traders and civic authorities must pledge themselves to practical efforts to use, retail and generally support Fairtrade products.
* For more information on the San Francisco Fairtrade status visit: http://bayareafairtradecoalition.blogspot.com/