the United States also includes a number of overseas territories. The main ones are Guam, Puerto Rico，and the Virgin Islands. America’s position on the globe and its relative position in relation to other countries both provide advantage for the country in its development. Main land America, lying within the northern temperate zone, grows large variety of agricultural products. The loi^ coastline with many harbors and inlets not only facilitates foreign trade and the fishing industry, but also bring much of the country within the influence of the oceanic air mass. America has no land nei^ibor which is strong enou^i to pose a threat to its security. This relieves the United States of the burden to maintain a large frontier army along its border. The two world wars played havoc with many nations. But they never spread into mainland America. As a matter of £act, Canada has been America's most important trading partner and the trade between America and Mexico is also climbing. The three nations have reached an agreement on establishing the North America Free Trade Agreement (NAFTA). There are sdll some technical problems remaining to be solved. But the door is open for wider cooperation based on mutual benefit.

So as the geographical features are concerned, the larg? territory of the continental United States can be divided into three basic areas：the Atlantic Seacoast west to the Appalachian Mountains；the great Mississippi Rivet Basin between the Appalachian and the Rocky Mountains; the Rockies west to the Pacific Ocean.

The Atlantic Seacoast West to the Appalachians

Along the Atlantic Seacoast is a narrow plain which begins far up the coast and becomes wider as it goes south. In the Northeast, the land extending to the Atlantic coastline is hilly, rocky and mostly infertile. Much of it is covered by heavy forests. The coastline, however, is broken by many excellent harbors which were once important centers of commerce and trade in the early days of the country. The Middle Atlantic Seacoast, the most densely populated region in the U.S. , is a flat and fertile region. Despite the fact that some of the largest cities in the world are situated here, there arc miles and miles beautiful, open country all through this section. Many heavily wooded mountains and deep valley cut by wide and beautiful rivers can be found. Three important rivers, the Hudson, the Delaware and the Susquehanna, flow throu^i this part of the country. In the deep south, the coast plain is very low and wide. The soil of this region varies greatly. Some parts along the coast are almost pure sand. Other sections contain some of the richest soil in the whole country. However, the weather, the land and the rivers that run through the south have made it, for most of its history, a great agricultural region.

The coastal plain 呼pears to be fenced in by the Appalachian Mountains that begin in Canada and reach all the way to Georgia and Alabama. These are old mountains with rounded tops and wooded hills, usually not exceeding 800 meters in height. Most of the mountain ridges are low enough to be easily crossed by modem roads. In parts of the Appalachians the land is not good for forming. But the Appalachians have much beautiful scenery, and there are many tourist resorts.