Walgreens is expanding its alcohol sales with its own beer called Big Flats 1901. The brand was launched quietly and is now available at more than 4,600 Walgreens stores. More of Walgreens’ 7,655 outlets will sell Big Flats 1901 when the outlets obtain alcohol licenses and the company said the new brew is already selling briskly. Walgreen Co. already sells two store-brand bottles of wine and expects to launch a third next month. Southern Point was launched in December 2009 and sells for $3.99 per bottle. A second brand, called David Stone, was launched in March and sells for $7.99. The next wine the store plans to introduce is to be called Colby Red, named after Australian winemaker Daryle Groom’s 12-year-old son, who was born with heart defects. The brand will be part of a promotional effort to raise awareness about heart disease.