PETALUMA -- After scrambling for months to keep up with skyrocketing national demand for its locally produced beer, Lagunitas Brewing Co. completed a four-fold, $15 million expansion of its Petaluma brewery in July.

The expansion will allow Lagunitas to produce up to 360,000 barrels a year, the latest benchmark for a growing craft brewer whose hop-laden beers helped launch a national fascination with strong and bitter brews.

"We were desperately short on beer at that point," said Ron Lindenbusch, head of marketing for Lagunitas who works under the title "beer weasel."

Last year, Lagunitas sold more than 160,000 barrels, Mr. Lindenbusch said. The brewery expects to sell more than 240,000 this year.

In addition to the new system, imported from Germany and assembled by Bavaria-based Rolec, Lagunitas will maintain its original 80,000 system for producing seasonal beers.

Yet more growth is on the horizon for Lagunitas, which plans to begin brewing from a second, 240,000-barrel-a-year facility in Chicago at the end of 2013.

"The reason behind Chicago -- Tony calls it 'Taking the diesel out of the beer,'" said Mr. Lindenbusch, referring to Lagunitas founder Tony Magee. "It costs a small fortune to ship east of the Rockies."