Geography Reference
In-Depth Information
It was only in the vast plains of the Middle West that the US was really able to
put into practice the geometric survey of the territory based on the parallels and
meridians of Thomas Jefferson's concept of
Township
.
3
The geometric grid, which
characterizes urban and rural areas, and was initiated in Philadelphia in the
eighteenth century, is a hallmark of the American landscape. In these immense flat
areas, it is the hydrographic system that determines the points of contact between
land and river transport, or the crossing points of major rivers where main cities
were built. The success of Chicago is therefore linked to its location at the southern
tip of Lake Michigan.
The eastern part of the territory is populated in a continuous and relatively dense
manner. This is first explained by the precedence of its colonization, but also by the
absence of any major natural obstacles.
West of the Mississippi, the environment becomes less friendly, especially
starting at the 100th meridian. The Great Plains rise gradually until they form the
foothills of the Rocky Mountains. The city of Denver is more than 1,600 meters
above sea level. These high plains differ from the lower plains of the Middle West
mostly by their semi-arid climate. The plains end abruptly at the barrier of the
Rocky Mountains. The Rocky Mountains are actually a series of separate mountain
ranges whose altitude do not exceed 4,400 meters. They mark the beginning of the
Pacific West region, whose topography is particularly rugged all the way to the
coast.
The irregular geology of fault blocks explains the juxtaposition of mountain
chains and basins, some of which form high plateaus and others very deep troughs.
This is why, for instance, the Great Salt Lake of Utah is situated at an altitude of
1,280 meters.
The highest point of the conterminous United States is Mount Whitney (4,417 m)
located in the Sierra Nevada in southern California, just 150 km away from the
lowest point located in Death Valley at 86m below sea level.
This irregular topography considerably impeded the progress of settlers in the
19th century. High altitudes combined with the land's general aridity explain the
very sparse population of the plateaus and basins of the inland regions of the West.
Apart from a few urban oases, the population of the West is concentrated along the
shores of the Pacific Ocean.
3
. Thomas Jefferson (1743-1826) is considered to be the father of the Declaration of
Independence of 1776. He was president of the United States from 1801 to 1809 and pioneer
of the country's expansion (in particular, the Louisiana Purchase from France, in 1803).
