The art of cheese making was brought to America by the English and the Dutch, followed by Germans and Italians, so most early cheeses made in America were modeled after these styles. Production and importation of raw milk cheese aged less than sixty days has been prohibited in the US since the 1940s. Most cheese at this time and for decades after was mass produced in factories using pasteurized milk. Artisanal, or hand made cheese, has become very popular over the past twenty years in the US. This new wave of American artisanal cheese makers has sparked some new controversy about the safety of raw milk cheeses.