What, Exactly, Is Gentrification? It’s hard to define, but it's dramatically changing the urban landscape and bringing a host of new challenges to local leaders. January 26, 2015 • series on gentrification, which appears online and in the February 2015 print issue. Ask the mayor of any reasonably successful medium-sized American city about his or her dreams for the city’s center, and you will nearly always get the same answer: The mayor dreams of a vibrant downtown, blessed with myriad dining and entertainment options; storefronts that attract high-end retail shopping; streets that are well-traveled and safe at all hours of the day and night; in the old neighborhoods just outside the center, long, pleasant blocks filled with stately pre-war houses restored by new owners to their original glory; and in the center, a sprinkling of luxury condominium and market-rate rental buildings attracting young couples lured by all the amenities a thriving city can provide.