MTTC History (009) Practice Test

The pattern is driven by climate and how the Cascade Mountains shape it. The mountains create a rain shadow, so the western side receives plenty of moisture and mild conditions, while the eastern side is colder and drier. Dense populations tend to concentrate where agriculture and daily life are easier, which means the wet, temperate western region supports higher population density. The harsher eastern climate makes sustained, large populations more challenging, leading to lower density there. Other factors like migration, land area, or mineral resources can influence settlement, but the climate difference best explains the east–west density contrast.