On a windy hilltop where mist and rain are as common as sunshine, a small distillery is turning out an experimental, hopped whiskey which has the potency of a hammer blow and a flavour to warm the hearts and tastebuds of connoisseurs.

On a windy hilltop where mist and rain are as common as sunshine, a small distillery is turning out an experimental, hopped whiskey which has the potency of a hammer blow and a flavour to warm the hearts and tastebuds of connoisseurs.

The 129.4 proof Charbay Double Barrel Hop-Flavored Whiskey may be a little on the pricey side - it sells at around $350 (£180) a bottle - but it is in the vanguard of a growing movement to create new, distinctive whiskeys.

The distillery producing it is not in Scotland or Ireland but in a vineyard above the Napa Valley in Northern California, one of a growing number of sites on America's west coast where distillers are challenging Scotland's long-held supremacy in the production of fine whiskys.

In the past few years six distillers have started making and selling whiskey in California and Oregon and several more are expected to join them in the next year or so.

"We certainly have the knowledge here because of the number of Scots who settled here and have brought their skills with them. Rye and bourbon were originally made by Scots and Irish immigrants," says Phil Elwell, who stocks more than 20 varieties of Scotch in his Ye Olde King's Head pub and restaurant in Santa Monica, California and is looking forward to adding California whiskey to his bar. "What makes Scotch whisky so good? They say it's the water. Well, we have great mountain water here, too."

The west coast is known for its wine and beer, which is precisely why many believe locally distilled whiskey is also catching on. "People in California have grown up with wineries and microbreweries so they are already receptive to craft whiskeys," Mr Elwell said.

All the distillers have at least one thing in common - they cannot call their product Scotch, even though at least one distiller specialises in a peaty, 80 proof whiskey that has been compared to an Islay malt. And unless it has been aged for at least three years in new charred oak barrels, California law mandates that they cannot even call it whiskey - it has to be described as "spirit." Stephen McCarthy, who produces McCarthy's Oregon Whiskey from his Clear Creek Distillery in the Portland area, says proudly: "Our whiskey would be a single-malt Scotch if Oregon were Scotland."

He uses a peat-smoked barley imported from Scotland and fermented into a "wash" or unfinished beer. "We don't hop it or finish it or do any of the other things done to finish a beer," he said. "Using the unfinished wash allows us to get all the flavour and character of the malt when we distil using our pot still. We then barrel-age the rough distillate in several kinds of oak barrels." After ageing the whiskey for two or three years in used sherry barrels, as would be done in Scotland, he finishes it in new barrels of Oregon white oak for six to 12 months.

"Oregon winemakers tried white oak for a while but they concluded it wasn't suitable for wine," he said. "I tried it as a lark and decided I liked what it did to the whiskey - it gave it a richer, more complex character."

The result is a smooth, peaty whiskey which is emphatically Scottish in style although, he says, "production is very limited because what I put in the barrel doesn't come out for years".

While most of the world's whiskey - apart from Scottish single malts - is made in high-volume, continuous stills that can produce thousands of gallons a day, the West Coast craft whiskey movement has gone back to the antique pot still. Although it is more labour intensive and a lot less productive, yielding perhaps five gallons per batch, it produces a more distinctive result.

A panel of wine connoisseurs assembled by the Los Angeles Times to taste several of the West Coast whiskeys concluded: "We were struck by the generally high quality and the wild diversity of styles." The tasting panel described McCarthy's Oregon Whiskey as "an aggressively smoky, peaty 80-proof whiskey with an iodine nose much like an Islay malt such as Lagavulin".

The only whiskey distillery in Southern California, St James Spirits, based in an industrial park in the Los Angeles suburb of Irwindale, also uses malt from Scotland, but owner Jim Busuttil combines Bourbon and Scotch techniques for his Peregrine Rock California Pure Single Malt Whiskey.

One of the most successful brewers was also the first to legally distil whiskey in California. The Anchor Brewing Company of San Francisco, whose Anchor Steam Beer was responsible for reviving craft beer brewing in the 1970s, is now hoping to kick-start drinkers' interest in the sort of rye whiskey that George Washington was making more than 200 years ago.

"Making barley whiskeys doesn't interest me but the fact that rye was the original American whiskey but went out of style and almost disappeared is something that really intrigues me," said Anchor's owner, Fritz Maytag. "When the Scottish and Irish arrived in the 18th century they began making rye whisky instead of rum, probably because it was cheap to make. But with the popularity of bourbon, rye faded away.

"When I read about George Washington and his rye whiskey, I became intrigued and thought I would like to try and recreate the rye that was the original American whiskey."

Using small, open copper stills like the one George Washington used, Maytag distilled his first batch of rye whiskey in 1994. "At the time no whiskey was being made legally that way in the US and I saw the chance to do in American whiskey distilling what I had done in brewing," he said. The first batch of rye went into the barrel in 1994 and for over a year neither Maytag nor anybody involved said anything about it. "We had our first taste of it in January 1996," he recalled. "It was a fine rye whiskey and I'm very proud of it."

When word leaked out, others followed Maytag's example, but Anchor is still the leading producer in California, selling several thousand cases of rye a year with plans to step up production as demand increases.

The whiskey movement continues to grow on America's west coast and while several new distilleries currently have whiskey ageing, another company plans to build a distillery in California near Yosemite where it will even grow its own barley.

"It's a wonderful new venture for California," Mr Elwell said. "Mark Twain wrote to his brother that: 'In California whiskey is for drinking and water is for fighting over.'

"Now it seems that here whiskey is for distilling, too."