Population density, or population per square mile, is a by-product of population growth, and indicates where growth occurs within the county. Monitoring changes in population densities provides an opportunity to assess land use in urban, suburban, and rural areas. Urban areas have population densities measuring at least 3,000 people per square mile, and are expected to have a concentrated mix of housing, retail, education, medical, recreation, and transportation options. Communities measuring below 1,000 people per square mile are rural areas, where residences and amenities are spread farther apart from each other, as the land is used primarily for agriculture, forestry, and horticulture. Population density impacts costs of service provision, as government and business investments are made based on the efficiency and expense of marketing, distributing, or serving populations over the expanse of a geographic service area.

Wake County is an urbanizing county. The population density grew by 43.5% between 2000 and 2010. In 2013 four Wake County municipalities ranked in the top 15 most densely populated in North Carolina: Raleigh (#3), Cary (#6), Apex (#8), and Morrisville (#11).

From 2000 to 2010, Morrisville had the greatest increase in population density of all Wake County municipalities, soaring from 770 to 2,249 persons per square mile.

The United States Census Bureau publishes official population estimates and population estimate revisions for prior years annually. County, state, and national data are released in March. Municipal data for population density are updated on census years only; the most recent census year was 2010.

January 2015: Revised to reflect 2013 census estimates