UNITED STATES OF AMERICA 



.V.lUi 



UNITED STATES OF AMERICA 



have been in the past, at the same time fur- 

 thering the development of all the countries 

 bordering the Pacific so as to benefit all parts 

 of the world. The United S kin? a 



merchant marine, permitted Europe practically 



a monopoly of trade with South America until 

 the completion of the canal and the outbreak 

 of the great war in 1914. Since then American 

 merchants have opened the way to profitable 

 trade relations with the southern republics. 



Size, Coast Line and Physical Features 



In the matter of size, among the continents 

 North America ranks third, after Asia and 

 Africa, while in the proportion of coast line to 

 area it ranks secondj being exceeded only by 

 Europe. The more indented the coast line, 

 the greater is the proportion of coast line to 

 area, and therefore the more abundant are the 

 opportunities for oversea commerce. In the 

 portion of North America included within the 

 United States, the proportion of coast line is 

 perhaps greater than for the continent as a 

 whole, especially along the North Atlantic 

 coast. This portion of the continent has sunk 

 somewhat in recent geological time, thus drown- 

 ing the lower vallej r s beneath the sea and caus- 

 ing innumerable inlets which form excellent 

 harbors. 



On the other hand, the South Atlantic and 

 Gulf coasts have risen somewhat in recent geo- 

 logical time, causing the sea to be shallow for 

 a considerable distance off shore and rendering 

 approach to the land difficult. On the Pacific 

 coast there are relatively few good harbors, 

 owing to the Coast Range, which rises directly 

 from the sea, the principal inlets being the 

 Golden Gate at San Francisco, the Columbia 

 River and Puget Sound, all of which penetrate 

 through the Coast Range to the interior valleys. 



Physical Features. The United States ex- 

 hibits most of the physical features found in 

 North America as a whole. There are five 

 main geographic divisions, as follows: 



(1) The Atlantic coastal plain, 



(2) The Appalachian highland, 



(3) The interior plain, 



(4) The Cordilleran Highland (see CORDIL- 

 LERA), 



(5) The Pacific slope. 



Each of these in turn comprises various smaller 

 subdivisions. 



The coastal plain is mostly submerged in 

 New England, the sea almost washing the foot 

 of the uplands, but it increases in width toward 

 the south, becoming broadest along the Gulf 

 of Mexico. This plain formed part of the 

 ocean floor in recent geological times, and the 

 rocks in it are still soft. The soil is sandy near 

 the sea, but clayey farther inland. Along the 

 inner edge of the coastal plain, where the rivers 



pass from older and larger rocks to the soft Cl- 

 ones of the plain, is a regular "fall line," that 

 is, a series of falls or rapids in the rivers. This 

 fall line, which affords water power and, in SOUK* 

 cases, forms the head of stream navigation, is 

 marked by a row of important cities, all the 

 way from Trenton, N. J., to Montgomery, Ala. 

 (See FALL LINE.) 



The Appalachian highland consists of four 

 belts, roughly parallel to each other, extending 

 from New England to Alabama. Just above 

 the fall line is a hilly district called the Pied- 

 mont (meaning foot-of-the-mountain), which 

 is much older than the coastal plain. This va- 

 ries a good deal in fertility, depending upon 

 the kind of underlying rock which by its decay 

 has formed the surface soil. In general, how- 

 ever, the Piedmont Region is fairly fertile, ex- 

 cept where the slope is so steep that the rains 

 have washed away most of the soil. West of 

 the Piedmont rises a mountain range known as 

 the Green Mountains in Vermont, the High- 

 lands in New Jersey, the Blue Ridge in Vir- 

 ginia, the Great Smoky and the Unakas farther 

 south. In general, however, it is usually called 

 the Blue Ridge. This range is quite steep 

 throughout the southern part of its course, but 

 has been cut through by a number of rivers, 

 forming water gaps. These gaps are of great 

 importance because they furnish routes for 

 highways and railroads at low levels. 



West of the Blue Ridge, again, is a belt of 

 lower land known in New York as the Hudson 

 Valley, in Pennsylvania as the Cumberland, in 

 Virginia as the Shenandoah, and farther south 

 as the valley of East Tennessee, but called as 

 a whole simply the Great Valley. This de- 

 pression, caused partly by the sinking of blocks 

 of the earth's crust and partly by a belt of soft 

 rocks which the rivers wore away faster than 

 the harder rocks on either side, extends all the 

 way from Canada to Alabama, varying greatly 

 in width, but averaging perhaps forty to sixty 

 miles. The bottom of the Great Valley is fairly 

 level, except where rivers have cut channels or 

 where smaller ridges of hard rock rise above the 

 general elevation of the surface. The soil has 

 been partly formed on the spot from the soft, 



