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Boundaries delineate the extent of areas.They define regions as having characteristics that differ from their neighbors. They divide one area from another. Boundaries are devised by humans or they follow natural features. The conterminous United States is divided from Canada by an international boundary that was the result of treaties with Britain. The Pacific Ocean sets a natural boundary around Hawaii.
Private properties, school districts, counties, Congressional Districts, postal and telephone area codes; these are all examples of regions divided, delineated, and defined by manmade boundaries. The boundaries of the United States were determined as a result of treaties, purchases, colonial charters, and acts of Congress. A property boundary is defined by a property deed and survey. Local administrative boundaries are typically decided by local and regional government organizations. Imaginary lines of latitude and longitude are also frequently used by humans to define boundaries. Of course, any boundary set by men and women can be changed by them as well.
Nature also sets and alters boundaries. The Continental Divide is a ridge line stretching from northwest Canada to northwest South America. It's a natural boundary dividing the waters flowing west from those flowing east or north. A river is a good example of a natural feature that also serves as a boundary between two areas of land. In some cases, humans have elected to use rivers and streams as administrative boundaries. For example, a section of the boundary between Oklahoma and Texas follows the course of the Red River. Since river courses can change quickly, using them as administrative boundaries isn't always a good idea.
Boundaries that are of national significance and use, that are fairly stable, and those that can be mapped at a small scale are included in the National Atlas. We have to consider what types of boundaries can be portrayed at our current map scale, which is 1:2,000,000. At that scale, an inch-long line on your computer screen represents nearly 32 miles on the land surface. Even if local municipal boundaries were relatively stable, many would be impossible to portray at the scale of the National Atlas. Here we've tried to assemble a variety of maps that are useful in understanding the United States as the sum of its parts. For example, you won't find local boundaries like voting precincts or school districts in nationalatlas.gov™. But you will find information about national voting patterns or educational levels that have been mapped at a county level of detail. You will find international, State, and county boundaries. Though these boundaries have changed over the years, they are now relatively stable. You will also find other administrative boundaries such as Federal lands and Congressional Districts. And you will find natural boundaries, such as watersheds and geologic contacts.
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Last modified: Monday, 14-Jan-2013 17:18:04 CST