With St. Patrick’s Day coming up, it may be time to party. But is it also time to banish the green beer and get serious about Irish sips?

For the growing number of drinkers who have discovered Irish whiskey in the past decade, the answer is clearly yes. The category is the fastest growing in the American spirits market — up nearly 400% since 2002 and 22.5% in the past year alone, according to the Distilled Spirits Council of the United States. And that growth is spurring a flurry of business ventures and acquisitions, often resulting in the release of new whiskeys.

Illinois-based spirits giant Beam Inc. acquired Ireland’s Cooley Distillery for $95 million in 2011 and has actively promoted several brands connected to it — most notably, Kilbeggan — that had previously received little exposure in the U.S. And Tullamore Dew, a popular Irish brand, is looking at launching a new $45 million production facility by 2014 and hopes to expand its line of releases in due time.

Irish Whiskey: America's new favorite sip

“These are very, very good days for Irish whiskey,” says Ken Reilly, a marketing director with William Grant & Sons, the Scotland-based spirits company behind Tullamore.

And then there’s Jameson, the world’s best-selling Irish whiskey, which is part of the family of spirits belonging to Pernod Ricard, the French liquor company. In recent years, it’s been heavily promoting itself with a series of television ads consciously designed to mimic an epic movie. (Adweek reported that the initial campaign cost $14 million.) It’s also benefitted from celebrity support: Lady Gaga has talked up the brand in concerts — she refers to it as “my boyfriend Jameson” — and Rihanna has worked a Jameson reference into a song.

In short, we’ve come a long way from the days when most American bars or restaurants had only one bottle of Irish whiskey on hand — and even then, it was often just used for making Irish coffee.

“I think Irish whiskey has been underestimated,” says Sean Muldoon, the founder and proprietor of The Dead Rabbit, a new upscale Irish-themed bar in New York City.

To look at Muldoon’s spirits menu — he believes he has one of the largest selections of Irish whiskeys in the U.S. – is to understand what he means. The choices go well beyond the few familiar bottles to include such select and high-priced whiskeys as Midleton Very Rare (for $38 a glass) and Knappogue Castle 1951 (for $250 a glass). As Muldoon describes the latter in his bar menu, it is a “take-no-prisoners whiskey that is beguiling and complex, with aromas of overripe bananas and molasses, and has palatal notes of apple, licorice, honey.” (Muldoon also likes using Irish whiskeys — albeit cheaper ones — in any number of creative cocktails.)

The boom, say spirits industry experts and insiders, has a lot to do with the growing interest in whiskey in general, from single-malt Scotches to good ol’ American bourbon. And in fairness, Irish whiskey has a long way to go to achieve parity with its counterparts from other countries — 2.2 million cases of Irish whiskey were sold in the U.S. in 2012, compared with 9.2 million cases of Scotch and 16.8 million cases of bourbon.

But the reason it has room to grow, say experts, is because it has a smoother, sweeter flavor profile than most other whiskeys — and is therefore much more readily appreciated by a younger generation of drinkers accustomed to white spirits like vodka and rum. It all boils down — almost literally — to how Irish whiskey is made: Typically, it’s distilled three times, whereas Scotch is distilled twice. (The distillation process involves boiling.)

The extra step helps even out the taste — perhaps not a positive for those who like a whiskey with a little more bite, but a welcoming factor for those who don’t want to have to “work” as hard when it comes to enjoying a glass. That said, Irish whiskey made in the pot-still style — with a mix of malted and unmalted barley in a particular type of still — is generally said to have more character and depth. (The Dead Rabbit’s Muldoon cites the Redbreast brand, also part of Pernod Ricard, as the quintessential example of a pot-still whiskey.)

But there’s more than a taste profile or an interest in whiskey in general that’s driving the Irish trend, especially in America, says Frank Coleman, senior vice president of the Distilled Spirits Council of the United States. There’s also the fact that the U.S. is a country with deep Irish roots, extending back to the wave of immigrants that started arriving in the 19th century and continuing with new arrivals today. Which means that when many Americans sip an Irish whiskey, they are enjoying a taste of home. “It brings a sense of authenticity to the table,” says Coleman.

The Dead Rabbit bar

But that sip is also undergoing something of a transformation. Different and new styles of Irish whiskeys are quickly finding their way onto the market. Several brands have now released single-malt whiskeys — much as one would find from Scotland — even though Ireland has generally been known for its blends (blended whiskeys tend to be smoother). And last year, Bushmills, another major Irish brand, released a flavored product: Bushmills Irish Honey. Demand is clearly there for these new styles. “We sold out of our entire initial allocation,” says Yvonne Briese, a brand manager at Diageo, the British spirits giant that owns Bushmills. (As might be expected, Bushmills has since produced plenty more of the honey-flavored whiskey.)

If there’s an irony to what’s happening with Irish whiskey, it’s that the trend is really a case of history repeating itself. A century ago, Irish whiskey was very much the whiskey of choice in many places throughout the world. But key events cut into demand — specifically, prohibition in America and Ireland’s independence from Great Britain (and the resulting effects on trade). “The largest markets (for Irish whiskey) were the British Empire and the U.S. and all of a sudden those two markets were eliminated,” says Bob Gorman, a marketing director with Beam Inc.

Now, Irish whiskey is back in vogue — in America and elsewhere. Still, St. Patrick’s Day is unlikely to give sales much of a boost. While Irish brands welcome any extra revenue, they say March 17 is not key to their marketing strategy. Instead, they’re finding success promoting Irish whiskey as an everyday drink, whether enjoyed straight or as a mixer. “It’s truly starting to become more year-round,” says Wayne Hartunian, a vice president for marketing at Pernod Ricard.