Hangar 24 Craft Brewery. Strange Brewing Co. Old Hangtown Beer Works. Peter B’s Brewpub.

These are four of the companies that donated beer to the 2011 Craft Brewers Conference and BrewExpo Trade Show, unfolding (as I write this) in San Francisco.

Don’t ask me where these breweries are located. I had never heard of them before the conference. But with 1,759 breweries currently operating in the United States — the most since 1900, says the Brewers Association, which organizes the annual conference — it’s getting near impossible to keep tabs on this industry.

It will get even harder. There are 618 breweries in the planning stages, says the BA’s director, Paul Gatza. Many of these would-be beermakers were among the 3,900-plus who attended the conference, shopping for equipment at the BrewExpo Trade Show and soliciting advice from their peers.

The BA passed over the young upstarts and chose two well-respected graybeards to deliver the conference’s keynote address. Forty-five years ago Fritz Maytag bought into a ramshackle brewery about to close and turned Anchor Brewing Co. into the model of a modern craft brewery. He sold the business last year but still runs a dairy farm and a vineyard.

Ken Grossman was a homebrewer and the proprietor of a bicycle shop in Chico, Calif., when he brewed his first commercial beer (five barrels of stout) in 1980 and set Sierra Nevada Brewing Co. off and running.

The two swapped memories of the 1970s and 1980s, an era when small, independent brewers were dwindling rapidly and analysts predicted that as few as two or three breweries might still be in business by 2000.

Maytag recalled beer conferences of 30-odd years ago peopled by reps of large national companies: “big, important guys in double-breasted suits and badges.”

“Some of their yachts were bigger than my brewery,” he added.

Grossman remembered scavenging through shuttered regional breweries looking for spare parts and feeling , despite a twinge of sadness at seeing these businesses close, “like a kid in a candy store.”.

The two collaborated last year on a beer dubbed Fritz and Ken’s 30th Anniversary Ale. Bottles of this big, roasty imperial stout were passed around, and we offered a toast — our first beer of the day — at 10:55 a.m.

There was excitement not only at the industry’s overall success (volume was up 11 percent in 2010), but at craft brewing’s latest convert: President Obama, who served a homebrewed honey ale at his Super Bowl party.

“This was a great step forward,” said guest speaker Peter DeFazio, Democratic congressman from Oregon and co-chair of the House Small Brewers Caucus. DeFazio mentioned that he and Grossman thought about sending a couple hop rhizomes packed in soil to the president for inclusion in the White House vegetable plot. They dropped the idea after a White House liaison told DeFazio that the Secret Service would probably intercept the package for fear it might be tainted with anthrax or some other contaminant.

DeFazio said he and Grossman would try again, offering the hops to the Department of Agriculture for its Independence Avenue garden.

Hops, perennial vines that can climb 10-15 feet or higher, are a fascinating plant, according to an exhibit staged by the Bavarian Hop Growers Association. They’re capable of growing up to 30 centimeters (about a foot) a day, and the plants can easily live as long as 50 years.

They’re a member of the family Cannabaceae, the same botanic grouping that includes marijuana. That’s not something you want to pop up on a background check.