Even this rule isn't always true. In Virginia a city can be independent, which means the city and county are the same government. It New England, where countie

Even this rule isn't always true. In Virginia a city can be independent, which means the city and county are the same government. It New England, where counties don't really have much power and the towns have the power that counties generally have in other States. Or Connecticut, where counties only exist because there are federal forms you cannot complete without listing a county. I am sure there are other exceptions too, but these are the places I have lived, and thus know.