John Wesley Powell (1834 - 1902, image above from Wikimedia commons) was made the first director of the Bureau of Ethnology in the United States in 1879, which was established that same year by an Act of Congress, a position he held until his death in 1902.  

That bureau, which changed its name to the Bureau of American Ethnology in 1897, was directly connected to the Smithsonian Institution, which had been established in 1846 through the will of the British chemist James Smithson (1765 - 1829) and funded by his bequest of 105 sacks of about 1,000 gold sovereigns each, and pursued the mission of organizing all the anthropological research in the nation.

In his first year as head of the Bureau of Ethnology, Powell submitted the first of his Annual Reports of the Bureau of Ethnology to the Secretary of the Smithsonian Institute, dated July 1880 and covering the Bureau of Ethnology's efforts for 1879-1880.  The entire report can be seen online here among other places.  

Beginning on page 73 of that publication is a famous essay by Powell entitled "On Limitations to the Use of Some Anthropologic Data."  In it, Powell sets forth the doctrine which would become the guiding principle of his Bureau of American Ethnology and of the Smithsonian at large all the way through the present day, a strictly isolationist doctrine which flatly declares that it is "illegitimate" to entertain any line of analysis which attempts to connect any artifacts found in the New World with any "peoples or so-called races of antiquity in other portions of the world."  

A reproduction of the letter, with the passages emphasizing this isolationist doctrine highlighted in yellow, can be found online here as well.

The motivations behind this strict imposition of the isolationist paradigm and flat rejection of the examination of any possibility of diffusionist explanations (which propose the possibility that there was contact across the oceans prior to the arrival of Columbus) can and have been debated.  Many biographers and vignettes emphasize the "tremendous respect" Powell had for the native tribes of North America and some have suggested that his support for an isolationist doctrine was based upon that respect for the Native Americans and the view that any theory proposing ancient pre-Columbian contact with "peoples or so-called races of antiquity in other portions of the world" must automatically be disrespectful to the native peoples here, or even based upon some kind of racist animus.  

It is certainly likely from some of the episodes of Powell's life that he did in fact have tremendous respect for the Native Americans.  However, it is undeniable that Powell's own 1879 essay displays some extremely paternalistic and disrespectful generalizations, including his assertions in the second part of the essay (entitled "Picture Writing," beginning on page 75 of the above-linked version of the 1879 report) that the "pictographs" found in North America are "simply the beginning of pictorial art" and in almost all cases "simply mnemonic" -- possessed of no systematic or as Powell calls it, "conventional," structure by which ideas could be preserved using symbols that possessed a common meaning agreed upon by all who understood that system (i.e., whose meaning was agreed-upon by convention across a large number of people, thus constituting a writing-system).  

In this astonishing denial of the existence of writing systems, Powell explicitly includes even the obvious writing-systems of the Maya and the Inca and other cultures of Central and South America, whose artifacts were by no means unknown to him and to the other employees of the Bureau of Ethnology (in fact, the 1879 report contains long sections dealing with "Central American Picture Writing," and many of the other annual reports discuss the artifacts and culture of the Maya and Inca and other civilizations in detail).  Nevertheless, Powell asserts in his letter that:
To some slight extent pictographs are found with characters more or less conventional, and the number of such is quite large in Mexico and Central America.  Yet even these conventional characters are used with others less conventional in such a manner that perfect records were never made.
Such a statement is extremely paternalistic, and effectively denies the existence of any true systematic writing systems, even among the cultures of Mexico and Central America!  Based upon this false assertion, Powell then declares: "Hence it will be seen that it is illegitimate to use any pictographic matter of a date anterior to the discovery of the continent by Columbus for historic purposes."  By this declaration, Powell effectively discarded any and all artifacts containing writing from consideration of historic analysis, and in doing so protected his earlier declaration that any contact with peoples from "other portions of the world" is plainly "illegitimate."  

Thus, none of the numerous inscriptions and artifacts which clearly attest to the possibility of ancient contact -- many of which have been discussed in previous posts on this blog and many more of which have been detailed in numerous published books -- could be considered as evidence which might challenge the isolationist dogma.  Some of those artifacts containing evidence of writing which strongly supports the possibility of ancient contact are discussed in the following previous posts:
And there are hundreds of other examples which could be discussed in addition to the evidence discussed in those posts.  To simply refuse to consider any such evidence at all is unscientific to the extreme, and yet it has been the implicit or explicit policy of the Smithsonian since the days of John Wesley Powell.

The fact that the Smithsonian has not changed their policy of refusing to consider any artifacts which might suggest the possibility of pre-Columbian trans-oceanic contact with the "New World" is evident from the controversy over the Bat Creek Stone found in 1889 in Tennessee, which the Smithsonian recently (early in 2014) called "an obvious fraud" in their response to Scott Wolter's discussion of the artifact on his America Unearthed program on the History Channel.  Scott Wolter's response to the Smithsonian's dismissive belittling of his examination of the Bat Creek Stone, and their ad hominem attacks on Wolter himself as lacking in "qualifications and reputation as a researcher," can be seen here.  His response also includes expressions of regret towards the Smithsonian's dismissal of the Bat Creek Stone from representatives of the Cherokee people, who did possess a system of writing and who told the Smithsonian that if they are so sure that the stone is a fraud, the Cherokee can take the stone back and rebury it where it was found out of respect to those who originally produced it.

Recently, a new aspect of the Smithsonian's policy of refusing to countenance any artifacts that might pose a challenge to Powell's "doctrine" of isolationism has received a lot of publicity in light of the publication of Richard Dewhurst's new book Ancient Giants Who Ruled North America: the Missing Skeletons and the Great Smithsonian Cover-Up (briefly discussed in this previous post).  Richard Dewhurst used the capabilities of modern search engines to examine the archives of US newspapers going back to the early 1800s and found hundreds of published descriptions of giant skeletons being unearthed across the North American continent, many of them containing photographs.  

He also found evidence that, while the Smithsonian in its early years was an enthusiastic documenter of such discoveries, the arrival of John Wesley Powell marked a dramatic change in the Smithsonian's attitude and policy towards such finds, to such an extent that Dewhurst was forced to conclude that: "What my research has revealed is that the Smithsonian has been at the center of a vast cover-up of America's true history since the 1880s" (3).  He documents numerous cases in which representatives from the Smithsonian arrived on the scene of any reported discoveries of giant skeletons with remarkable rapidity (sometimes within one or two days, even in the late 1800s and even when the archaeological find was in remote regions of the American west) and in which skeletons reported as being turned over to the Smithsonian were never seen again.  

Today, if one searches the internet for the terms "Smithsonian cover up," the predominant results will have to do with the cover-up of giant skeletons.   Richard Dewhurst believes that the motives for what he calls the "Powell doctrine" of suppressing and denying any archaeological evidence that could indicate the presence of other ancient peoples in the Americas or contact with ancient cultures from across the oceans may have sprang from the fact that John Wesley Powell's father was a Methodist preacher in Palmyra, New York (Powell himself was obviously named after John Wesley, 1703 - 1791, the founder of Methodism), where Joseph Smith first published the Book of Mormon in 1830 and where the early enthusiasm of the people of the area for the new revelations caused Powell's father to lose his congregation (as Richard Dewhurst explains in a footnote on page 6 as a likely motive for Powell's animus towards any diffusionist theories).

Richard Dewhurst also believes that the distasteful US policy of "Manifest Destiny" and the efforts of the federal government following the Civil War to seize the territory to the west of the Mississippi and to suppress the Native Americans who lived there played a role in the Smithsonian's (and Powell's) desire to characterize the native peoples of the continent as primitive barbarians, incapable of producing anything more than "the most rudimentary picture making," (Dewhurst, 6).  Dewhurst proposes that such a doctrine may have been deployed in order to help convince the population to support the aggressive plans to exploit the lands of the Native Americans.

If so, then the "Powell doctrine" probably did not originate with Powell himself, but would have likely been the determined policy of a number of other government officials.  At the front of Powell's first annual report (containing his essay declaring as "illegitimate" any attempts to connect any artifacts found in the New World with cultures from anywhere else) is an introductory letter from Powell to Spencer F. Baird, the Secretary of the Smithsonian Institute, in which Powell says the following: 
Sir: I have the honor to transmit herewith the first annual report of the operations of the Bureau of Ethnology. 
By act of Congress, an appropriation was made to continue researches in North American anthropology, the general direction of which was confided to yourself.  As chief executive officer of the Smithsonian Institution, you entrusted to me the immediate control of the affairs of the Bureau.  This report, with its appended papers, is designed to exhibit the methods and results of my administration of this trust. 
If any measure of success has been attained, it is largely due to general instructions received from yourself and the advice you have ever patiently given me on all matters of importance.
I am indebted to my assistants, whose labors are delineated in the report, for their industry, hearty co-operation, and enthusiastic love of the science.  Only through their zeal have your plans been executed.
Much assistance has been rendered the Bureau by a large body of scientific men engaged in the study of anthropology, some of whose names have been mentioned in the report and accompanying papers, and others will be put on record when the subject-matter of their writings is fully published.
I am, with respect, your obedient servant,
While this introductory and dedicatory letter may simply be an example of "polite formalities" or conventional platitudes within a government bureaucracy, in keeping with the style and traditions of the period, it is also possible in light of the topic being discussed that it contains evidence that Powell's doctrine did not originate with Powell himself, but was part of a policy transmitted by the Secretary of the Smithsonian Institution whose office was in Washington, DC, and of other men in Washington as well.  The highlighted areas (all highlighting is my own and is not found in the original document) seem to support such a possibility, with Powell referencing a "general direction" which "was confided" to the Secretary of the Smithsonian Spencer Baird by some unnamed parties (presumably parties connected with Congress, whose authorizing act for the creation of the Bureau of Ethnology was mentioned immediately prior to this mysterious assertion), and "the advice you have ever patiently given me on all matters of importance," and his declaration that "your plans [have] been executed."

The likelihood that what Dewhurst calls "the Powell doctrine" has roots far deeper than Powell himself (or even Powell's animus towards diffusionist theories due to the loss of his father's congregation) is evident from the fact that the Smithsonian's policy of refusing to entertain any possibility of ancient contact across the oceans and its haste to declare any artifacts containing inscriptions which might employ the known writing systems of ancient Mediterranean cultures as frauds or hoaxes has continued long after the death of John Wesley Powell, and continues to this day.  

This continuing refusal to examine artifacts containing inscriptions such as those mentioned in the list of previous posts above and reflexive labeling of such artifacts as either fraudulent or the products of post-Columbian contact cannot be explained by the Powell family's personal experiences in Palmyra, New York.  Nor, it seems, can the benighted and repulsive nineteenth-century belief in "Manifest Destiny" be the reason that the Smithsonian continued to enforce the "Powell doctrine" throughout the twentieth century, long after the United States had seized all of the lands of the Native Americans between the Mississippi and the Pacific Ocean, and most of the citizens of the country had forgotten that their land had once belonged to someone else.  Is it possible that there is some other motive which lies behind the Smithsonian's ongoing policy of anti-diffusionism?

Personally, I am not an expert on the "giant skeletons" controversy.  While it certainly seems, based upon the prodigious volume of reports and descriptions and even photographs (see, for instance, the photograph below from 1940 published in the San Antonio Express), that such skeletons have been found throughout the Americas in some numbers, and that the absence of any such skeletons on display at the Smithsonian National Museum is suspicious, I also believe it is a mistake to focus entirely on giant skeletons when talking about a "Smithsonian cover-up."  

The easiest way for defenders of the Powell doctrine to deflect such cover-up arguments is to argue that such "giant skeletons" were simply the remains of some isolated individuals exhibiting traits of giantism, to point out that enthusiasm over giants and the possibility of ancient trans-oceanic contact was rife in the nineteenth century (much of it fueled, it must be noted, by religious agendas and a desire to support literalist interpretations of the Bible or by the newly published Book of Mormon), and to argue that whatever skeletons may have been uncovered in those early decades were lost or crumbled to dust and were not maliciously squirreled-away in the bowels of the Smithsonian's warehouses.  

I certainly do not agree that these counter-arguments settle the case, and believe that Richard Dewhurst's analysis of the evidence of giant remains (and other such analysis by other researchers, such as the analysis in this essay found in several places on the web) is extremely valuable and worthy of careful consideration.  I also believe that all dogmatic declarations that the facts of the matter are settled and that no further analysis is legitimate (whatever the subject) should be treated with great suspicion (see discussions to that effect in previous posts such as this one, this one, this one and this one, for example).  Nevertheless, I also believe that the "giant skeleton" aspect of the "Smithsonian cover-up" question could become a huge red herring which falsely divides the debate in the eyes of the general public into two camps, those who believe America was once home to a race of giants, and those who generally side with the Powell doctrine.  

The Powell doctrine excludes a whole lot more evidence than giant skeletons, as the recent Bat Creek Stone controversy demonstrates.  There is abundant evidence that there was ancient contact across the oceans, most of it involving human beings of what we might call "normal" (or at least non-gigantic) stature.  As far as I know, no one is maintaining that the giants whose skeletons have been found throughout the Americas were the authors of inscriptions using known "Old World" writing systems including Hebrew, Egyptian (both hieroglyphic and hieratic), Phoenician/Punic, Ogham, cuneiform, runic, Iberian, Libyan, and Roman, but many of these have been found in the Americas and conventional scholars either ignore them, declare them to be frauds or hoaxes, or explain them away as artifacts which were brought to the Americas by Europeans after Columbus and either lost or given to Native Americans (this is the explanation for the small cuneiform tablet which Chief Joseph had in his possession when he surrendered to the US Army, described in this previous post linked above).  Many other forms of evidence for ancient trans-oceanic contact have been found, such as the amphorae at the bottom of Guanabara Bay in Brazil, and the mummies and other evidence listed in this previous post describing the "Calixtlahuaca head" (which is itself another artifact attesting to ancient trans-oceanic contact).

To the extent that the Powell doctrine and the ongoing policy of the Smithsonian and the rest of conventional academia ignores or devalues these artifacts, and discourages their honest appraisal by professional scholars, the search for the truth is greatly inhibited.  What professional scholar wants to risk ridicule and marginalization by publishing an examination of any of these pieces of evidence, at least one that reaches conclusions which contradict the oppressive official policy of the Powell doctrine?

Clearly, the so-called Powell doctrine did not originate with John Wesley Powell alone, and its ongoing enforcement throughout academia (and at the Smithsonian) is evidence that its roots go far deeper than John Wesley Powell himself.  Its continuing effect of suppressing open-minded examination of the evidence cannot simply be explained by Powell's personal views of the Native American peoples, or the personal impact his family may have experienced due to the "lost tribes" enthusiasms of the nineteenth century in general and the beginnings of the Mormon religion in particular.  Nor can its continuing impact be attributable to the nineteenth-century doctrine of "Manifest Destiny" (although perhaps related to the latest incarnation of that vicious doctrine).   

I believe that there is a bigger reason why powerful forces believe that evidence of ancient trans-oceanic contact must be suppressed, one that involves the spreading of illusions about history which powerful interests find extremely valuable for the public to accept.  The control of history can certainly be a form of very powerful mind control -- and the single-mindedness evident in the efforts of John Wesley Powell (and of the Smithsonian Institute since 1879) demonstrates just how important this control of history must be to someone's agenda.