That’s what Harvard scholar Samuel Arbesman found when he created this map. It shows the 14 states with more than half their total populations living in one Census-defined metropolitan statistical area:

Interesting, no? But the map doesn’t actually do justice to Rhode Island’s city-state-ness.

Turns out Rhode Island is the only state with its entire population in one metropolitan statistical area. New Jersey is a distant second, with only 73% of its population in an MSA, and Massachusetts is No. 9 with 63%. (Every resident of Washington, D.C., is in one MSA, too – but D.C. isn’t a state, so there.)

If you want more technical details on how Arbesman crunched the numbers to make the map, head over to his blog. Here’s how he described what he found:

[T]here’s not much of a pattern to this. For example, New York, Massachusetts and Rhode Island all grew out of single large population centers that were colonized early on, and this might appear to be a reason for being a city-state. However, Georgia does not have a similar history and is a city-state. On the other hand, Utah was also primarily colonized in a single city, yet is not a city-state.

More generally, these city-states don’t fit a single category in my mind: they are on both coasts as well as being landlocked, and encompass the non-contiguous states of Alaska and Hawaii.