Widespread use of air conditioning eventually facilitated a long-term shift in the U.S. population. Prior to home AC units, cities in the desert, the Deep South and Florida had very little growth as most people couldn't handle the oppressive weather. With the advent of home air conditioning, however, people were able to spread out and migrate to these formerly avoided areas. Today, some of the hottest cities in America — such as Phoenix, Arizona; Las Vegas, Nevada; and Dallas, Texas — continue to see population growth, thanks to air conditioning.