Most often when you cross the borders of a city or town, nothing much happens. Those edges, invisible lines of jurisdictional separation, are easily ignored or forgotten as we walk, bike, and drive through a metro area. Cities can blend into one another almost imperceptibly. Development just keeps going and going in many parts of the U.S., creating urbanized entities much grander than a single city. When we think about cities, it’s increasingly inaccurate to think about them in isolation.
Our ever more interconnected, urbanized world therefore presents a challenge to academics and researchers who aim to quantify and better understand cities. Where does a city really begin and end? These days there are as many ways to measure a metro area as there are arguments for and against each one.