[2] Hahn grew up in Wiehre, Germany and studied microbiology at the University of Freiburg and wanted to bring traditional German beer to the United States.
[3][4][5][6] Eventually, Hahn and Greiner founded Rosenstadt Brewery in 2015, making beer that follows the traditional Reinheitsgebot German purity law.
[2] At first they experimented at Max's Fanno Creek Brew Pub in Tigard, Oregon, where they developed a Kölsch which became one of their signature beers.
[6][7] However, Max's Fanno Creek Brew Pub was not equipped for making German beer, so they had to find another facility.
[2] After four years, Rosenstadt had nearly 300 accounts and made specialty beers for certain customers, including Clyde Common.