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Show X90o] PHYSIOGRAPHY I I until they disappear in the richness of vegetation brought about by the increased rainfall of Mexico and Central America. sThey are not an unbroken expanse of level territory^ but are often hilly and almost always rolling in character. The deep valleys cut by the intersecting streams further break the monotony of the region. The excessive dryness of the plains has prevented any large growth of population, but the discovery that they afford admirable grazing for horses, cattle, and sheep has brought about a development of that industry which has been of great significance in the growth of the United States and in the westward movement. ^ Xlje prairies, the remarkably fertile lowlands of the middle west, are seen at their best in the states of Iowa, Illinois, and Indiana, but extend well into Ohio, and were the chief attraction to early migration from the Atlantic states. - „ East and south of the Appalachian barrier lies a narrow strip of lowland, the Atlantic coastal plain, the seat of much of the early colonization. The water boundary of the plain is shallow, and from New Jersey to North Carolina is fringed with reefs which have forced the commercial settlements of the strip back upon the estuaries of the rivers draining the slope. " - South from the Carolinas the Atlantic plain sweeps around the southern end of the Appalachian Mountains and merges into the coastal plain of the Gulf, which in turn extends south along the Texas |