Which is the newest city in the US?
honolulu
Honolulu dates from the 12th century.
Centennial, Colorado was incorporated February 7th, 2001. With
over 100,000 residents, it was the largest incorporation in US
history at the time. One of its biggest problems was the refusal of
the US Post Office (as well as UPS) to recognize the city.
I'm sure there are newer cities incorporated in the ensuing 10
years, however.