The beginning of the craft beer revolution in the US revolved around imported European traditions that were influenced by the availability of raw materials in the US. The scarcity of original English hops and malts led to differences in flavors, even when original practices were maintained, and one of the most significant differences was the difference in hop flavor. The hop was far more aromatic in the southern United States than in the English countryside or continental Europe. One of the most historically important American hops was Cascade, which was introduced in the 1970s and for many decades became the most defining flavour of American beer styles such as American Porter.