Nutter assumed the post Saturday at the organization's annual meeting in Orlando and gave his inaugural address entitled "Moving America's Cities Forward."
Mayor Nutter said cities now have less money and fewer people to provide services, and he called that "our new normal in America."
He cited innovative efforts by cities across the country to address the challenges, including Philadelphia rethinking how it uses water.
And he cited the "Cities United" effort to combat urban violence that he said "is wiping out a generation of young, African-American men.
However Nutter said cities are the "future of America" as centers of new ideas, hubs of culture and art, and places "where people want to live and work."