In which American city, almost all the population lives in a single building?

The Begich Towers Condominium is a building in the small city of Whittier, Alaska, about 58 miles (93 km) southeast of Anchorage . The structure is notable for operating like a small-scale arcology, being the residence for nearly the entire population of the city (the 2016 estimate was 214 people), as well as containing many of its public facilities. This has earned Whittier the nickname of a "town under one roof".