No one wants their city to become a sprawling, ugly mess. So why do so many cities end up that way, and why is it so difficult to reverse the trend? A combination of economic and political factors make for a wall of resistance against “building smart,” and city zoning codes and neighborhood objections (also known as the Not-In-My-Backyard phenomenon) play a significant role in slowing responsible urban growth. As a result, only the most doggedly determined urban planners ever see their visions come to fruition in American cities.