Arizona Valley's Growth Redefines 'Edge'

"Growth has redrawn the Valley's traditional boundaries, pushing past mountain ranges, riverbeds and even county lines, forging a metropolitan area of more than 9,200 square miles that is bigger than seven states, including Massachusetts. What was once an orderly spread through easily defined suburbs now follows no predictable course.... 'We're on the edge of what's habitable,' said Phoenix attorney Grady Gammage, author of the book Phoenix in Perspective. 'In my lifetime, the nighttime low temperatures in the summer have risen by 11 degrees. If we continue to urbanize so that it continues to get hotter, that'll be a limit.'"