By density

Neil Freeman, 2006-7
database
dimensions vary

This tool uses US Census 2000 data to illustrate the distribution of the US population over ranges of population density. The database contains all 208,125 block groups in the 2000 Census. In 2000, block groups had a median area of 0.48 square miles (1.25 sq. km) and a median population of 1,133.

classing method required
units
number of intervals
density range optional, equal interval only
to
confine to a state optional, equal interval only

Densest block group

block group 1 in census tract 279, New York Co., New York
3,240 people
0.0097 square miles (6.2 acres)
326,814 people per square mile
510.65 people per acres

Median block group

(half the population is in denser block groups)
block group 2 in census tract 321, Mercer Co., Pennsylvania
1,373 people
0.54 square miles (349 acres)
2,521.6 people per square mile
3,22 people per acre

Least dense block group

block group 1 in census tract 3, North Slope Borough, Alaska
8 people
3,246 square miles (2,077,370 acres)
0.002 people per square mile
0.000003 people per acre