This region seems to have been one of the principal centres from which their settlements were advanced into the western part of Virginia; into Michigan, Wisconsin, Iowa, Illinois, Indiana, and Missouri. The spread of their settlements was necessarily gradual, and a long period must have been required to extend them over all the country where remains of their works are known to exist. If their civilization was chiefly developed after their arrival in the country, which is unlikely, many years must have elapsed before colonies went forth, to any great extent, from the original seat of its development. In any case, time was required to make their chief settlements sufficiently old and populous to send forth colonies. It is manifest in their remains that the communities of this ancient people most remote from the populous centres on the Ohio, east, north, and west, were, like all border settlements, the rudest and least populous. The remains at these points do not indicate either as much wealth or as many workers, and the places where these borderers settled must have been the latest occupied and the earliest abandoned. One diligent investigator, who believes they came originally from Mexico, speaks of the time of their stay in the country as follows:
“When we consider the time required to people the whole extent of the territory where their remains are found, and bring that people into a condition to construct such monuments, and when we reflect on the interval that must have passed after their construction until the epoch of their abandonment, we are constrained to accord them a very high antiquity.”
He points out that they were sun worshipers, like the Mexicans and Peruvians, and calls attention to the disks dug from their mounds, which appear to have been designed as representations of the sun and moon.
Their long occupation of the country is suggested by the great extent of their mining works. All who have examined these works agree with Colonel Whittlesey that they worked the Lake Superior copper mines “for a great length of time.” How long they had dwelt in the Ohio Valley when this mining began can not be told, but a very considerable period must have elapsed after their arrival at that point before the mines were discovered. We can not suppose the first settlers who came up from the Gulf region to the Ohio Valley went on immediately, through the wilderness a thousand miles, to hunt for copper mines on Lake Superior; and, even after they began to explore that region, some time must have passed before the copper was found.