Armed with a family recipe and a flair for marketing, C. James “Jim” Koch popularized craft beer in the U.S. and turned Boston Beer Co. into the third- largest American-owned brewery. It also made him a billionaire, as sales of his flagship Samuel Adams brand helped Boston Beer shares double in the past year and reach a record high Friday.

Craft beer such as Sam Adams has been a bright spot in an otherwise stale U.S. beer market. Total American beer sales fell 2 percent in the first half of 2013, according to data compiled by Bloomberg, while the craft brew segment grew 15 percent. Boston Beer’s sales increased more than 17 percent during the period.

“What he has done is amazing,” said David Geary, president of D.L. Geary Brewing, a craft brewer in Portland, Maine, he co-founded in 1983. “He’s very focused, a brilliant marketer and he sort of taught us all how to sell beer.”

Through a combination of in-person proselytizing and folksy TV ads, Koch created widespread awareness in the 1980s and 1990s that there was more to beer than what the major U.S. brewers and European imports were offering.

Consumers have flocked to Boston Beer’s 70-plus offerings, including its most popular seller, Boston Lager, to small batch specialty brews, such as Norse Legend, a Finnish-style sahti that Vikings drank. The demand has sent Boston Beer shares up ten-fold since mid-2009, propelling Koch’s net worth above $1 billion, according to the Bloomberg Billionaires Index. He has never appeared on an international wealth ranking.

Niche Market

“Having watched my stock price go up and down and up, it seems almost whimsical,” Koch, 64, said in a telephone interview. “I remind people getting rich is life’s great booby prize. Any normal person would much rather be happy than rich.”

Selling craft beer has made Koch both. This week, Koch will travel to Los Angeles and Maine, where he will go bar-to-bar trying to persuade beverage managers to carry Sam Adams, something he has done since he started brewing beer in his Newton, Massachusetts, kitchen in 1984.

“Because this was something started out of passion, I’ve been able to sustain 30 years of growing the business with all the ups and downs,” Koch said.

‘Better Product’