Additional Information on Coastal Areas

What is a coastal county?

As defined by NOAA, a county is considered a coastal watershed county if one of the following criteria is met.

1. At a minimum, 15 percent of the counties total land area is located within a coastal watershed or
2. A portion of an entire county accounts for at least 15 percent of a coastal cataloging unit. (i.e., an individual drainage basin).

This definition does not require a county to contain any coastline, nor does it require counties to be within a certain distance of a coastline. Some coastal counties, such as San Bernardino, CA contain no coastline and extent hundreds of miles inland.

In 2005, there were 673 coastal counties in the 50 states and the District of Columbia, grouped here into 5 regions: North Atlantic (Maine through Virginia), South Atlantic (North Carolina through Miami-Dade County, Florida), Gulf of Mexico (Monroe County, Florida through Texas), Great Lakes, and Pacific.

Population Growth in Coast Counties

In the 1950s the percentage population increase for coastal areas was more than twice that of non-coastal areas. Since then, percentage gains have been more similar for the two areas. Non-coastal areas have higher rates of population growth in the 1970s, 1990s, and post-2000 era.

Percentage Increases in Coast and Non-coastal Population by Time Period

The overall population increased between 1950 and 2005 was 106.1% for coastal areas and 75.8% for non-coastal areas.

Since 1970, the coastal counties share of the population has remained at a relatively stable 53-54%.

Demographic Components of Population Change: 2000 to 2005

The 6.9 million coastal population increase was due entirely to natural increase (births minus deaths) and international migration.

Much of the net domestic out-migration from the coastal areas was from only a few large counties. Fourteen populous counties had net domestic out-migration of 100,000 or more between 2000 and 2005; collectively, their net domestic out-migration totaled 3 million people.

(Density calculations exclude Alaska whose large coastal land area skews national analysis of population density).

19 of the 20 US counties with the highest population densities are coastal; the noncoastal exception is St. Louis city Missouri, whose population density of 5,561.1 ranked it 16 nationally.

In the South Atlantic and Gulf regions, many coastal counties with already high population densities have continued to grow. In the northeast and Midwest, the most densely populated coastal counties often contain older industrial cities such as Cleveland, Detroit, or Milwaukee and have little or no population growth in recent decades.

How many people live within 50 miles of coastline?

As of Census 2000 this 50-mile zone contained:

• 137.5 million people (48.9 percent of the U.S. total)
• 55.4 million housing units (47.8 percent of the U.S. total)
• 1.7 million seasonal housing units (48.1 percent of the U.S. total)

Note: For this calculation, the coastline was any land that borders the ocean and any of its saltwater tributaries, including bays and tidal rivers, and the Great Lakes. Excluded from this boundary were coastal rivers and lakes. (Therefore, the tidal Potomac and the Chesapeake Bay were included, for example, while the Hudson River and Lake Pontchartrain were not.) Once the coastline was delineated, a buffer was applied to identify all block groups located either partially or fully within 50 miles of this coastline boundary.

Seasonal Housing in Coastal and Non-coastal Areas

Between 1970 and 2000 the number of seasonal homes in the United States increased from one million to 3.6 million. Of the 2.6 million gained, 1.4 million was in coastal counties and 1.2 million occurred in non-coastal areas.

In 2000, seasonal homes represented 3.3 percent of all housing units in coastal areas, up from 1.6% in 1970. Seasonal homes constituted 2.9% of all housing units in non-coastal areas, up from 1.4% in 1970.

Between 1970 and 2000 the number of seasonal housing units in coastal counties increased by 237 percent, somewhat less than the 267 percent increase for non-coastal areas.

Source: Decennial Censuses of 1950, 1970, and 2000; Population Estimates Program’s 2005 Estimates. The data are subject to nonsampling error, which may be introduced during any of the various complex operations (editing, reviewing, or handling questionnaires) used to collect and process Census data.