Influxes of African, Asian, and Latino Americans helped Houston's metro area avoid economic stagnation. Could an expected demographic shift on the national level end up reviving other troubled cities? Houston is a window into the future of America. In 1970, the city was an oil town that was about one-quarter black and three-quarters white, with just a smattering of folks of other origins. Since the oil-price bust of 1982, however, growth in the city and metropolitan area has come almost entirely from influxes of African, Asian, and especially Latino Americans. These new Houstonians came to work in construction and service,...