1,000 feet above the level of the sea, and below 5,000 feet altitude nearly ninety-nine per cent of the inhabitants of the country find their residence. At great altitudes but few people are permanently residing. One sixth of the people live less than 100 feet above the sea-level. These, of course, reside along the seaboard and in the swamp and level regions of the South. Those living between 2,000 and 2,500 feet above the level of the sea are found largely on the slope of the great Western plains. Mr. Gannett finds that between 4,000 and 5,000 feet above the sea, but more especially between 5,000 and 6,000 feet, the population is greatly in excess of the grade or grades below it; and he attributes this appearance to the fact that the densest settlement at high altitudes in the Cordilleran region is at the eastern base of the Rocky Mountains and in the valleys about Great Salt Lake, which regions lie between 4,000 and 0,000 feet elevation. In this great region the extensive settlements at the base of the mountains in Colorado are to be found between 5,000 and 6,000 feet above the level of the sea. The mining operations above 6,000 feet, being restricted to the Cordilleran region, largely located in Colorado, New Mexico, Nevada, and California, account for the existence of the population at the altitude of 6,000 feet and more.
The population of the country is increasing numerically in all altitudes, but the relative movement is toward the region of greater altitudes, and is more clearly perceptible in the regions lying between 1,000 and 6,000 feet above the sea. The population is densest along the seaboard, the narrow strip containing our great seaports, as might be supposed; but the density diminishes, not only gradually but quite uniformly, up to 2,000 feet, when sparsity of population is the rule.
If we examine the population relative to latitude and longitude, it will be found that within those degrees in which are located the great cities the greatest density of population occurs, as, for instance, the area between 40° and 41° and longitudes 73° and 75°, containing the great cities of New York, Brooklyn, and Jersey City, with an aggregate population of 3,653,000 inhabitants; the single square degree between latitudes 42° and 43° and longitudes 71° and 72° degrees contains Boston and its suburbs, with 1,233,000 inhabitants, and that square between latitudes 39° and 40° and longitudes 75° and 76° holds Philadelphia, with 1,414,000 people. The square of latitudes 41° and 42° and longitudes 87° and 88°, which contains the larger portion of Chicago, has a population of 950,000. It is difficult to present the facts relative to the distribution of population in accordance with latitude and longitude for the whole country in this summary statement of salient points.
The distribution of population relative to mean annual rainfall indicates not only the tendency of people to seek arable lands.
