The signs of their culture are everywhere: elderly women with flowing skirts and ethereal smiles, children who wear tie-dye T-shirts and sandals. The hippies drew bright university drop-outs, Vietnam draft-dodgers, even a few veterans. Most are in their fifties now -"intellectual mutants", one local prosecutor dubbed them - people who believed marijuana, not to mention a few other drugs, was good for the soul.
Even by California standards, Humboldt, part of the "Emerald Triangle" and probably the most famous marijuana-growing name in the US, operates by its own rules. A glossy "directory of well-being" offers acupressure for dogs in Arcata, a small coastal town and the only place in the country where the Green Party controls the local council. The latest trendy herb, it is said, is St John's Wort, a naturally occurring anti-depressant described as a "herbal prozac".
The region is the spiritual birthplace of Earth First!, environmental zealots whose defence of the few giant redwoods left by the loggers make British campaigners such as Swampy seem tame. Tourists flock in. The radio stations play Arlo Guthrie and, of course, the Grateful Dead.
Humboldt's wilder days came in the 1980s, when the hippies began selling pot and triggered a minor goldrush to the region. Champagne flowed from jeroboam bottles sold in local stores, and sewing clippers used to trim the marijuana buds were sold by the candy racks at supermarket check-out lines.
Fifteen years of helicopter drug teams swooping from the sky to flatten, burn and confiscate crops have taken their toll. But the marijuana trade still sustains a class of landed gentry - and a network of defence lawyers charging $10,000 a case.
Last November Californians voted themselves the right to grow and smoke "medical" marijuana under Proposition 215 for virtually any ailment. The result is that back porch and basement pot gardens are flourishing while the wholesale price has slumped from a peak of $5,200 to anywhere between $2,000 and $4,000. As the harvesting season begins in Humboldt this year, buyers from the cities are not showing up.
"There's pretty widespread paranoia about the end of the commercial feasibility of marijuana right now," said one veteran Humboldt grower. On the other hand, he said, there are renewed hopes that the marijuana trade will be legalised.
"The most common comparison is to the wine industry," said the grower, who gave up a promising academic future for a fantasy of growing fancy vegetables in the country. "A bottle of wine can be $2 or $50. It's up to the individual to produce high quality, and Humboldt County is capable of that." He got into the business 20 years ago when offered a suitcase of cash for the marijuana seeded with his aubergines. He remembers laughing at the unreality of it, throwing the notes in the air, even burning them in his stove. He has made about $200,000 since, off a modest annual crop.
America is not about to decriminalise pot. About 80 per cent of people oppose it. Government officials insist marijuana is the gateway drug, used in a mixture with crack, and teenage use is soaring. But at the same time, about 65 per cent of Americans back marijuana being made available to alleviate cancer, Aids and other illnesses.
Proposition 215 allows Californian residents to "obtain and use" marijuana when it is recommended by a doctor for anything from glaucoma to migraine. It gave an illegal drug the status of a common painkiller but made no provision for its supply, except from a pot plant.
The result has created glorious and very Californian confusion, and has made marijuana users bolder than ever. In Los Angeles last week, one 27- year-old man was busted for growing 4,000 marijuana plants on the grounds of his Bel-Air mansion. His family and friends, outraged by his conviction, said he was a victim of cancer and a self-taught scientist who bred new strains of marijuana for fellow sufferers.
About 300 hundred miles to the north, in San Jose, officials of the local Medical Cannabis Centre are negotiating with police to open the first marijuana dispensary licensed by a city government. They have been offered a permit if they keep their distance from churches and schools. Similar buyers' clubs, ostensibly for medical users, have opened in Los Angeles, Berkeley, and other California towns.
In San Francisco the biggest and brashest club is run by a man who insists all marijuana use is medical, and claims to have issued "contracts" to hundreds of growers. The problem is that buying, selling and growing marijuana, except by patients or their primary care givers, remains a serious crime. California's Republican Attorney General, Dan Lundgren, says the clubs are illegal, though none has been raided since April.
Humboldt farmers these days use isolated greenhouses equipped with generators. If not, their outdoor plants blend into trees and other vegetation.
Mom and Pop growers plough their earnings back into hilltop mansions powered by solar panels. The young get-rich-quick types, often hippies' children, are nicknamed Knights of The Toyotas for their slick four-wheel drives. The trick, they say, is never to be caught at your patch.
KMUD, a local radio station, broadcasts daily updates on the whereabouts of helicopters and police road blocks. Drug teams concentrate on destroying crops, knowing juries are apt to acquit on the slimmest defences. And under 215, there is the medical defence. "They are not going to argue with sick patients," said attorney Ron Sidoway.
"I haven't seen people this excited about marijuana since I was in high school," says another Humboldt grower. The man sits outside his hillside home with a copy of High Times, the marijuana magazine, and a sandwich bag of cannabis on his table. Along with a joint, he offers a vial of brown stuff he calls cannabinden, which he describes as extract of pot, smokable with a pipe. Both are respectfully declined.
Nervously, he gives a tour of his greenhouse, with 20 plants worth up to $100,000. He brandishes a piece of paper on which is written: "The marijuana in this greenhouse is being grown in accordance with California law under Proposition 215 for the exclusive use of the Berkeley Cannabis Buyer's Club." But he, too, complains about the price: "I'm not going to deliver it to town at the price that they want to pay."