Downtowns are more than economic engines: they are repositories of knowledge and culture and generators of new ideas, technology, and ventures. They are the heart of the city that drives its future. If we are to have healthy downtowns, we need to understand what downtown is all about; how and why some American downtowns never stopped thriving (such as San Jose and Houston), some have been in decline for half a century (including Detroit and St. Louis),...