 The combined Interstate 15/Interstate 84 runs northward in the eastern part of the county.The two routes diverge at Tremonton, with I-84 heading northwest past Snowville into cenral and western Idaho, and I-15 heading north past Plymouth and Portage into eastern Idaho.As of the 2000 United States Census, there were 42,745 people, 13,144 households, and 10,804 families in the county.