In the class I’m teaching this semester, Cities and the Environment, we’ve been debating the merits of urbanization from a sustainability perspective. One thing that is becoming clear is that density matters — it helps to determine the efficiency of resource use, the proximity of jobs and amenities, and the utility of public transportation. In general we’ve been zeroing in on the idea that more dense urban areas are likely to be more sustainable, or that density in general is a “good thing.”
With this in mind I read a list of the 5 densest cities in the U.S., and according to Census data from 2010, they are:
1. New York
2. Los Angeles
3. San Francisco
4. Trenton-Ewing, N.J.
5. Honolulu
This list is unlikely to coincide with general notions of the 5 most sustainable cities in the U.S.; it doesn’t coincide with mine.
So obviously it’s not as easy as “greater density leads to greater sustainability”…but maybe density generates more opportunities for sustainability; maybe it’s a better starting point. Maybe it depends on what your notion of sustainability is.
More on this as class progresses!

That the list of dense cities from the census seems improbable (excludes Chicago, for instance) would prompt me to ask if the census defines cities the same way we intuitively do.
Dan Fraikin
Great point — I know there is some effect from the “weighted density” metric they use. Will be looking into this!