Until a few years ago, the opinion was quite general, even among historians and ethnologists, that the mounds were built by a race of people who lived in the Mississippi basin before the coming of the Indians, and that the mound builders were far superior to the Indians in civilization. Many thought that this prehistoric race had been driven southward by the Indians, and that the Aztecs whom the Spaniards found in Mexico and Central America four hundred years ago were its descendants. We have in Wisconsin a reminder of the Aztec theory, in the name Aztalan, early applied to a notable group of earthworks in Jefferson county. There were many reasons why, in an earlier and more imperfect stage of our knowledge concerning Indians, this theory seemed plausible. It was argued that to build all these mounds required a vast deal of steady labor, which could have been performed only by a dense population, working under some strong central authority, perhaps in a condition of slavery; that these people must have long resided in the same spot; and must have been supported by regular crops of grain, vegetables, and fruit. It was shown that Indians, as we found them, lived in small bands, and did not abide long in one place; that their system of government was a loose democracy; that they were disinclined to persistent labor, and that they were hunters, not farmers. Further, it was contended that the mounds indicated a religious belief on the part of their builders, which was not the religion of the red men. The result of these arguments, to which was added a good deal of romantic fancy, was to rear in the public mind a highly colored conception of a mythical race of Mound Builders, rivaling in civilization the ancient Egyptians. But we are living in an age of scientific investigation; scientific methods are being applied to every branch of study; history has had to be rewritten for us in the new light which is being thrown upon the path of human development. This is not the place to set forth in detail the steps by which knowledge has been slowly but surely reached, regarding the history of the once mysterious mounds. The work of research is not yet ended, for the study of ethnology is only in its infancy; nevertheless, it is now well established that the Indians built the mounds, and we may feel reasonably certain for what purpose they used them.