When the Baltimore Orioles host the first game of their American League Division Series against the Detroit Tigers later today, local fans will carry the rituals they held throughout the season into the playoffs. They will shout "O!," for Orioles, when the national-anthem singer reaches the word; they will dance to "Thank God I'm a Country Boy" during the seventh-inning stretch; and throughout the game they will toast their team with countless cups of National Bohemian beer, or Natty Boh, as it is affectionately known. "Crabs, O's, and Boh's" goes the often-repeated list of summertime pleasures on the Chesapeake Bay.

Natty Boh is an inexpensive American adjunct lager, like Budweiser or Coors. Though not highly regarded among beer lovers (it has a rating of sixty-seven—"Poor"—on BeerAdvocate.com), Baltimoreans cherish the brew. Ninety per cent of Natty Boh's sales are in Charm City. Drive through Baltimore on I-95, and you will see the black-and-white visage of Mr. Boh, the beer's one-eyed, mustachioed mascot, peering down like Dr. T. J. Eckleburg on the neighborhoods of Brewers Hill and Canton. All across town, billboards and T-shirts celebrate the symbiosis between Natty Boh and Baltimore: Edgar Allan Boh, Old Bay seasoning and Boh, special purple-and-silver Ravens cans of Boh. Some even refer to the city as Bohtimore.

All of this civic affection might lead you to believe that Natty Boh is a local product. But although the beer can trace its origins to nineteenth-century Baltimore, every drop of Natty Boh consumed today at Camden Yards and in the rest of the city is brewed at plants in Georgia and North Carolina, by Miller Brewing, whose parent company, SABMiller, is South African. Last month, it was announced that the brand's owner, Pabst, is being purchased by the Russian beverage company Oasis, in partnership with the private-equity firm TSG Consumer Partners. According to the Wall Street Journal, the deal values Pabst—which also owns Schlitz and Old Milwaukee—at more than seven hundred million dollars. The acquisition is the latest in the consolidation of the global beverage industry. Nearly half of the world's beer is sold by four corporations: Anheuser-Busch InBev, SABMiller, Heineken, and Carlsberg. More consolidation is expected: it was reported last month that Anheuser-Busch InBev is seeking financing to buy rival SABMiller.

In Maryland and elsewhere, this trend has been countered by the growth of microbrewing. The Brewers Association has reported that small and independent American brewers saw their share of the U.S. beer market rise from 6.5 per cent, in 2012, to 7.8 per cent, in 2013. Craft brewers have gained this traction in part by adopting many of the practices of the locavore food movement, offering seasonal beers and products made with regional ingredients, often linking their identities to the locales where they are made. Some of these microbrewers have been critical of the fact that Natty Boh has been so thoroughly embraced by the citizens of Baltimore, when it is, in fact, owned by a multinational conglomerate. Last year, Maryland craft brewer Heavy Seas released a T-shirt with the image of a pirate that bears a more-than-passing resemblance to Mr. Boh. On the back, the shirt reads, "Actually brewed in Baltimore." Asked about Natty Boh by the Baltimore Sun last week, Hugh Sisson, the founder of Heavy Seas, replied, "I don't think there's a local brewer who doesn't want to roll their eyes."

National Bohemian hasn't been locally owned since the nineteen-seventies, and it hasn't been brewed in Maryland in more than a decade. Its origins do lie in Baltimore, however. It was first brewed, in 1885, by the newly founded National Brewing Company, as part of a thriving nineteenth-century brewing industry in the city. The brewery was forced to shut down during Prohibition, but returned, in 1933, under the ownership of the Hoffberger family and flourished for the next three decades, becoming one of the twenty largest brewers in the country. The Hoffbergers introduced a new recipe, modernized production, and, in 1943, became the first beer producer to sell its product in six-packs.

In 1953, National Brewing's president, Jerold Hoffberger, helped to bring the St. Louis Browns to Baltimore, where they changed their name to the Orioles. To assuage the Griffith family, who owned the nearby Washington Senators and opposed the sale of the Browns to a group of Baltimore investors, Hoffberger offered to have National Brewing sponsor Senators games on radio and television. A dozen years later, he purchased a controlling stake in the Orioles and assumed chairmanship of the team. Under Hoffberger's ownership, the Orioles went on to win two World Series and four American League pennants. It was during this heyday that National Bohemian became the "official" beer of both the Orioles and the city of Baltimore.

Both National Brewing and the Orioles passed out of Hoffberger's hands in the nineteen-seventies. For the next three decades, the National Bohemian brand languished, purchased first by Stroh, then G. Heileman Brewing, and then by Pabst, in 1999. Pabst, which capitalized on the affection of city-dwelling hipsters for its Blue Ribbon beer in the first decade of the century, used Natty Boh's legacy in Baltimore to cultivate similarly passionate devotion among young Marylanders. On social media, they share pictures of their Mr. Boh tattoos, their Bohtinis (Natty Boh with Old Bay seasoning on the rim), and their encounters with the Mr. Boh mascot. During the 2012 playoffs, the @NattyBohs Twitter feed (an account that is not officially linked to the beer) was a hub of Orioles fandom. It is likely to be so again this October.

Late last week, I dropped by Nacho Mama's, the unofficial Natty Boh headquarters in Baltimore, for a drink. In 2011, when Natty Boh was made available on draft after an absence of more than a decade, the first keg was tapped there, and, last year, Natty Boh issued a commemorative can to honor Patrick "Scunny" McCusker, the restaurant's proprietor. When I arrived, the room was littered with bottles and pitchers of Boh.

I spoke with two employees, Sean Fisher and Kallie Amentas, who told me that sales of National Bohemian had been rising steadily in recent years. They doubted that the acquisition of Pabst by Oasis would change that trend. "It is still a Baltimore beer," Fisher said. "It almost defines us."