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North America at night. Satellite image of the Earth at night, set against a background of stars, centred on the continent of North America. North is at top. City lights (yellow) show areas of dense population. The highest concentrations of population are on the West and East coasts, in cities such as San Francisco and New York. Inland, the continent is well-developed in the east, but the Great Plains and the Rocky Mountains form a band of sparsely populated land in the west. The cities of Mexico, the Caribbean and north-western South America are at lower right. Northern Canada and the Arctic (top) are largely uninhabited. Image data obtained in 2001 by the Defense Meteorological Satellite Program (DMSP). (KEYSTONE/SCIENCE PHOTO LIBRARY/NASA/NOAA)