(In) the industrial cities of 100 years ago ... millions of...

(In) the industrial cities of 100 years ago ... millions of urban dwellers ... were obliged to endure cramped and unsanitary tenements, traffic and pollution-choked streets and deadly factories. Today, by comparison, most residents of affluent metropolitan areas live in relatively low-density suburbs, areas that are much cleaner, greener and safer than the neighborhoods their great-grandparents inhabited.