That it has the word city in its name does not necessarily make it a city.

Here's a couple of sites that seem to indicate that the legal definition of city in the US is a little hazy.

http://mage.geog.macalester.edu/apgeogdemo/acity.html

http://www.gweep.net/~sfoskett/mqp/mqp_fin2.html#ToC10

It's probably the case that different states and maybe even different counties have different definitions for city.