James Fallows, writing for The Atlantic:
By national standards Sioux Falls is small-ish, but it’s the biggest city in the state and has increasingly become the regional metropolis — the place where people come to do their shopping, get their medical care, and in many cases pursue their business ambitions.
What’s new here isn’t necessarily the phenomenon, but rather the cities that find themselves in this position. Today it’s Duluth, but yesterday it was Minneapolis-St. Paul. As population grows, once marginal cities take on new importance.