• This map shows the growth of the US population from 1790 to 2010, with each circle representing a county. Counties on the ocean coast are highlighted.


• I did not produce this map. The original is found in the public domain at the United States Census Data Visualization Gallery. I converted it into a gif format with some slight modifications.


• Here is what the page said:
  
  In 2010, the percentage of the population living in a county with a coastline was comparable to what it was between 1790 and 1800, when the US still relied heavily on trade with European markets and access to interior lands was limited. In the intervening decades, the percentage of the population living in coastline counties decreased to an all-time low in 1880. A steady increase led to a recent peak in 1990, and a slight decrease since then has led to 2010's level
  
  Counties are based on 2010 geography and historical populations are based on population estimates derived from decennial census data. Point locations are based on population-weighted county centroids. Values in the data table have been rounded to the nearest thousand. The graph showing the percentage of the population living in a coastline county in each decade is based on unrounded figures.

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