Population density is the average number of people per unit of land area. In the U.S., the most common unit of population density is persons per square mile. The land area measurement excludes lakes and other water areas within.

1. April 1 Population density and land area criteria used for rural area assistance and other programs
2. References to population density in Washington law
3. Estimates of April 1 population density
   1. Tables
      1. State and county, 1900-2020 by decade, postcensal 2021 to present
      2. City and towns, 1980-2020 by decade, postcensal 2021 to present
   2. Maps
      1. County, 1900-2020 by decade
      2. Census block, 1990-2020 by decade