There are 3,140 counties in the United States. 21% (673) are classified as coastal. More than half of the U.S. population lives in a coastal county. The entire state of Hawaii is now included in the coastal zone (previously state forest reserve lands were exempt).

Coastal areas are home to a wealth of natural resources, and they also sustain a wealth of economic activity. They are home to some of the most developed areas in the nation. Although population increase and coastal development produce numerous economic benefits, they also may result in the loss of critical habitat, green space, and biodiversity. In 2003, 23 of the 25 most densely populated U.S. counties were coastal.

The nation’s coastal population is expected to increase by more than 12 million by 2015. Coastal population growth is generally the same rate as the entire nation, but in the limited space of coastal counties. This increasing density makes the task of managing coastal resources increasingly difficult. Public policymakers in coastal counties are confronted with the task of finding a balance between benefiting from economic growth while mitigating the effects of this growth on coastal environments. Population Trends Along the Coastal United States: 1980-2008 ~US Department of Commerce, NOAA

All of Hawaii’s counties are coastal counties.