I do this activity with my Geometry class during a unit of Volume as a fun and interesting research activity to show how population density (population/area) and density (mass/volume) are related. I use Milwaukee, Wisconsin, and the United States in the activity, but it could be easily adapted to your home town and state. To pique their interest, I also show this video beforehand:
We generally have some discussion after watching it to talk about what it made them think about, etc.
Another interesting resource that goes along with this activity: