The whole west is dry. See on that second map in post # 1. Draw a north-south line through San Antonio, Austin, Dallas/Ft Worth, Oklahoma City, Wichita and on northward. To the right of that line there is yellow. To the left of that line it's more green. That's the dry line. People can't live where there is no water. With the exception of a few places like Seatle, there is very little rainfall west of that line. The southwest has been reckless in the way they have encouraged population and economic growth to the point of severely stressing the water supply. The northwest either has not tried to excede sustainable population or more likely has tried but has failed to attract more people. The lower population level of the northern plains and Rocky Mountains is much more environmentally sustainable.