Population density, or population per square mile of land area, is a by-product of population growth, and indicates where and how much 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, horticulture, or open space and parks. 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 51% between 2000 and 2012, from 755 to 1,140 persons per square mile. In 2012 four Wake County municipalities ranked in the top 15 of the most densely populated cities in North Carolina: Raleigh (#4), Cary (#7), Apex (#9), and Morrisville (#13).

Between 2000 and 2012, Morrisville's population density increased by 224%, the highest increase among all core municipalities in Wake County.

The United States Census Bureau publishes official national, state, and county population estimates and population estimate revisions for prior years annually in March. Municipal estimates are published annually in May. Data is published here on or around March 30 by Wake County Planning, Development, and Inspections.

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