INTRODUCTORY. 



The monuments left by prehistoric races in the United 

 States are much more numerous in the eastern part of 

 the Mississippi valley than over the "Western Plains. 

 This is plainly shown on a map issned some years ag'o 

 by the Bureau of Ethnology and prepared to exhibit 

 the geographical distribution of prehistoric works east 

 of the Rocky Mountains. * From the Mississippi river 

 and eastward, the localities of mounds and other pre- 

 historic works appear numerous and crowM.led, while west- 

 ward from the great river they are few and scattered. 

 Evidently in prehistoric times as at present the more 

 fertile and more richly watered eastern plains afforded 

 a more congenial environment to the inhabitants than 

 the less favored western country. In another respect, 

 also, the monuments of early man in America bear wit- 

 ness to a comparatively small population in prehistoric 

 times westward from the great liver. On the Western 

 Plains we find none of those magnificent earthen struc- 

 tures, that were erected by the prehistoric people of the 

 Ohio valley and b\- tliose who dwelled near the Missis- 

 sippi. The conditions of existence in the west evidently 

 did not result in the development of such powerful com- 

 munities as could spare the energy needed for the con- 

 struction of great momids. 



* Catalogue of Prehistoric Works east of the Rocky Mountains, by Cyrus 

 Thomas, Smilhsonian Institution, Washington, D. C, 1891. 



