Five principal classes of wheat are grown: hard red winter (HRW), hard red spring (HRS), soft red winter (SRW), white and durum (Table 1.2). Most HRW wheat is grown in the central and southern Great Plains states; most HRS wheat is grown in the northern Great Plains states; and practically all SRW wheat is grown in the east. White wheat is grown primarily in the Pacific Northwest and white winter wheat in two eastern states, Michigan and New York. Most durum wheat is grown in the northern Great Plains, primarily North Dakota; some durum is grown in southern California and Arizona. There has been recent interest in growing hard white wheat in the central states of the Great Plains. About 41 percent of the total US wheat production is of the HRW class.