There were about 5.6 million cases of hard cider sold in the U.S. in 2011. At the same time, mainstream beer sales are down.

While cider still makes up only a tiny fraction of the U.S. alcohol industry, small producers are sprouting up across the country, and the nation’s two largest beer companies have recently entered the cider market.

Hard cider isn’t new. In the 1700s and 1800s, it was the drink of choice for early Americans. But as German immigrants brought their beer-making skills to America, cider fell out of favor.

The drink’s popularity took another blow in the 1920s, during Prohibition, when alcoholic beverages were banned in the United States.  But today, hard cider is making a comeback.

Bob Caloutti, who sells beer and wine in Rutland, Vermont, carries several brands of hard cider.

It is a small niche market, he says, but sales are growing fast among men and women.

“Oh, I definitely think the potential is there," Caloutti says. "Cider has been around forever and then if you throw in the gluten-free aspect, there’re a lot of people who can’t have gluten, which is obviously a common factor in beer, so I think cider is here to stay.”

The bestselling cider in America is Woodchuck Amber, which has been made in Vermont since 1991. 

“When I started with the company way back when, all we heard was, ‘No.’  People didn’t know what hard cider was," says Bret Williams, who heads The Vermont Hard Cider Company, which makes Woodchuck and handles three other brands of cider. "Now I’m worried about whether we can keep up with demand and make enough product.”

At the Vermont headquarters, Williams walks past bottling equipment that sterilizes, fills, caps and labels nearly 600 bottles of cider per minute. Still, because it's hard to keep up with demand, this summer construction began on a new $24 million headquarters which will more than double the company’s output.

“In this economy, to be talking about any growth at all is pretty amazing," says Williams. "The fact that we’re growing by over 30 percent annually and we needed an entirely new building is phenomenal, and I pinch myself every day, and that’s been going on the last five years.”

Woodchuck’s popularity has helped spur an explosion of small craft cider producers across the country. Major beer companies do not want to miss out.

MillerCoors recently purchased the Crispin Cider Company of Minnesota, while Anheuser-Busch recently launched Michelob Ultra Light Cider.

“When the major players get involved in a category, we’re going to bring a lot of interest to the segment,” says Paul Chibe, vice president of marketing for Anheuser-Busch.

How much major companies will help grow the fledgling cider industry is unclear.  The U.S. cider market is small, less than one percent of the beer industry. That is nothing compared to Britain, where cider makes up more than 15 percent of the beer market.

Chibe says it is unlikely the U.S. cider market will ever grow that large.  Still, he sees tremendous potential.

“When you look at the profiles, you think about consumers’ interest in variety," he says. "You see how big the white wine segment is in the U.S. and its broad appeal. There’s no reason why cider can’t be significantly larger in our market.”

That growth is something the Vermont Hard Cider Company is counting on. Despite adding a third shift, the company can hardly keep up with demand.

“The product that you see on the conveyor right here is going to go on that pallet," Williams says. "The fork truck is going to pick it up and it’s going to go right on a truck and it’s out the door.”

Their new expanded bottling facility will help. But Williams already expects to expand again in three-to-four years.