Over the past 30 years the Yuengling Brewery has vastly expanded its footprint, serving 15 states from Massachusetts to Florida, thanks to its wildly popular lager.

The place where it all began, the original brewery on Mahantongo Street in Pottsville, continues to operate not only as a brewery, but as a museum of the history of "America's Oldest Brewery."John Callahan is Yuengling's brewery manager, overseeing the brewery in Pottsville and another in Saint Clair. He rose through the ranks over the years, starting as an apprentice in the days when Yuengling was known more for its "Premium" beer than lager, which was only introduced in 1989.At the Pottsville brewery, he oversees the production of about a half million barrels every year. In addition to lager, the brewery produces Porter, Lord Chesterfield Ale and Yuengling Premium Beer.All of the beer from Pottsville is put into cans, kegs and quart bottles.While lager is far and away the brewery's most popular beer, Callahan says that locals still prefer the Premium, which is Yuengling's oldest beer. Up until a few years ago, it was still sold in returnable bottles."You go to a bar around town here and ask for a Yuengling, you'll get a Premium," he said.All of the Yuengling bottles sold in Pennsylvania are made at the Saint Clair plant, which produces about 1.5 million barrels per year. That is also where the brewery's new seasonal beers - Summer Wheat, Oktoberfest, and the recently introduced India Pale Lager, are produced.The 16- and 24-ounce cans are actually produced at Yuengling's Florida Brewery.Unlike virtually every other brewery in the United States, the Pottsville facility is built vertically. While Yuengling's other breweries are highly automated, in Pottsville most of the process is the same as it has been since Prohibition.The process starts on the top floor, where barley, corn and water are cooked into a liquid known as "wort" in huge, 600-barrel kettles. That takes about eight hours.The original copper kettles have since been replaced with stainless steel.From there, hops and yeast are added, and the beer is put into another set of tanks to ferment for about a week.The yeast and temperature are manipulated to create the beer's unique flavor - up until this point, the recipe is virtually the same as other brews."The yeast is very sensitive; it's like a big baby," Callahan said.Used yeast and barley are usually sold to farmers. The barley makes great feed.If the process stopped here, the beer would be considered an ale. But Yuengling stores the beer a second time, at a lower temperature, in a process known as "lagering." For many years that process took place in huge caves that are dug into the rock underneath the brewery. Today, modern refrigeration is used, and caves are only used for tours.After the beer is canned or kegged, it is sent directly to distributors around the area, meaning that the beer you buy at stores around Pennsylvania usually came off the line just a couple weeks earlier."Beer, it's not like wine," Callahan said. "The fresher the better. You gotta drink it fast."