**COURTESY OF FR. F. ANTONELLI, O.F.M.**
The United States, excluding Alaska and Hawaii, extends from 25° to 49° N. lat. and from 67° to 125° W. long. It is bordered by Canada to the north, the Atlantic Ocean to the east, Mexico and the Gulf of Mexico to the south, and the Pacific Ocean to the west.
The eastern part of the country is dominated by the Appalachian mountain system, which consists of parallel ridges separated by wide longitudinal valleys. It extends for approximately 1,600 km with a width of 70-200 km, rising slightly above 2,000 m and retaining an appearance more of medium than high mountains, with rounded ridges and valleys and gentle slopes. The Appalachians are bordered toward the nearby coastline by a plateau (Piedmont) which is followed by a series of waterfalls (Fall line) at the coastal edge (Coastal plain). This plain narrows from south to north, where it is indented by wide bays corresponding to the lower valleys of the major rivers (Hudson, Delaware, Chesapeake).
The western highlands, incomparably more extensive, consist of at least three mountain ranges, one of which is inland and stretches from the Canadian border to the Rio Grande (Rocky Mountains), and two near the Pacific coastline, separated from the first by a series of plateaus of varying character (the basaltic plateau of the Columbia to the north, the arid plateau of the Colorado to the south, cut by deep canyons, and, between the two, the Great Basin, a vast complex of elevations and depressions, dotted with swamps and salt lakes). Despite their height (numerous peaks exceed 4,000 m), not even the Rockies resemble the Alps closely here: the forms are, as a rule, gentler, and, due to the relative scarcity of rainfall, there is less abundance of water, glaciers, and forests. On the other hand, the double mountain range that rises along the Pacific is abundantly watered by the southwestern sea winds; therefore, the elevations are covered with magnificent forests and glaciers are more frequent locally. A series of wide valley troughs (Great Valley of California, Puget Sound) separates from the outermost coastal ranges that, rich in volcanoes, take the name of Cascade Range (Mount Shasta, 4,390 m) and the Sierra Nevada (Mount Whitney, 4,420 m), which continues it to the south.
The central plains, which essentially constitute the basin of the Mississippi, deserve this name only in correspondence to the lower course of the latter; for the rest, and especially between the Mississippi and the Rockies, they include a wide plateau, which the river's tributaries divide into fragments isolated by deep valleys. Approximately the 100th meridian W. Greenwich distinguishes here an eastern region, more humid and suitable for cultivation (Prairies), from a western one where the steppe dominates, essentially pastoral in vocation (Great Plains).
The notable variety of topographical conditions is naturally accompanied by climatic differences; however, most of the U.S.A. (east of the Rockies) is characterized by temperate-continental regimes, with rainfall predominantly in summer (in winter in the southern states), decreasing from the Atlantic toward the west. In the internal plateaus, these conditions intensify, determining sub-desertic or desertic climates, while in