The German filled doughnut has a different name in every region. Berliner in the north, Krapfen in Bavaria and Austria, Kreppel in Hesse, Pfannkuchen in Berlin itself, and in the American Midwest, a bismarck. The earliest known jelly-filled recipe is in a Nuremberg cookbook from 1485.
Fastnacht means the eve of the fast. In southern Germany the day before Ash Wednesday was for using up the lard, sugar and butter before Lent, and the doughnut was how you did it. German immigrants carried the word and the custom to Pennsylvania, where it became Fastnacht Day, and then along the roads west.
This trail stays out of Lancaster County, which has its own. It follows German immigrant family bakeries instead: a Bavarian who opened in Philadelphia twelve days after his wedding, a Thuringian who sold doughnuts from an alley in Hagerstown, a Black Forest farm boy fired from a Columbus bakery who built his own, a Swiss village in West Virginia that burns Old Man Winter at midnight. In Louisville the line ends in a neighborhood called St. Joseph, where the Germans settled and the bakeries stayed.