Ross Hamilton is the author of The Mystery of the Serpent Mound: in Search of the Alphabet of the Gods (first published in 1993), a book exploring new aspects of the Great Serpent Mound (located in Adams County, Ohio) which came to light through the efforts of various researchers in the 1980s.

Using a very accurate map of the Serpent Mound published by Harvard archaeologist William F. Romain in 1988, Mr. Hamilton determined that the Serpent Mound appears to possess a remarkable correspondence to the stars of the constellation Draco.  The argument for an identification with Draco, along with excellent diagrams, can be seen here.  More elaborate discussion of the same theory can be seen in this article, which was linked in this previous blog post.

He says in his book (on page 93):
The universal fame of Draco is closely related to its domination of the heavens thousands of years ago, and has, as such, influenced scripture and philosophy more than is generally understood.  The very term "philosophy" carries at its hear the terms "ophi" and "soph" related to serpent and wisdom respectively.  The Serpent Mound was apparently constructed on the basis of this constellation, albeit with careful thought, enabling its design to take into its folds many other aspects of the arts and sciences.
One of the most intriguing aspects of Mr. Hamilton's argument is his observation that, when the stars of the constellation Draco are superimposed upon the layout of the Serpent Mound,  the star Thuban (or α-Draconis) falls right in the center of the first serpentine fold of the body below the head.  

In one of the essays linked above, Mr. Hamilton explains that his discovery that one of the stars did not fall somewhere on the raised mound of the serpent (all the others do) initially caused him to doubt his hypothesis that the Serpent Mound might have been intended to represent Draco.  However, when he learned more about the important identity of that particular star (Thuban), and that it had once been the pole star in an ancient epoch, it led him to an important new discovery:
It was noticed that nearly every star nicely fell upon the outline of the effigy except the one beneath the first coil from the head. That star was no less than Thuban, noted above. It was a little disarming at first, because I didn't know what the star was and felt that the constellation's alignment with the earthwork was jeopardized by the fact of this one lonely star not 'fitting in' to my theory. I felt like just another pseudo-scientist trying to 'make' something fit that in reality didn't fit. Then, when the discovery of its being the ancient Pole Star sunk in, I took a good steel compass, and using that point of Thuban beneath the coil as the swivel point, extended the ink tip to the tip of the earthwork. Upon finishing the circle-arc, I noticed that the tail was nicely encompassed. That's when the realization came that the design of the earthwork was Thuban-centric. The dating took the design back to the time that the Pyramids were being constructed on the Giza plateau.
A diagram of the "Thuban circle" that he drew with Thuban as the center-point can be seen on that same essay linked above.  I've created a version of the concept in the diagram below:

In the diagram, the location of Thuban is marked with a star.  A circle centered on that point neatly encompasses both the triangular mound located in front of the "egg" that the serpent is devouring (difficult to see on the above diagram) and the outermost spiral of the serpent's coiled tail.

Mr. Hamilton asserts that if the mound was designed to imply a circle with Thuban at its center, and if we know that Thuban was once the pole star -- marking the celestial north pole, around which the entire heavens appear to rotate -- then this implies that the Great Serpent Mound was designed to refer to that epoch during which Thuban was the pole star!  This is a remarkable and controversial assertion, but it is a logical possibility based on the discovery of the existence of this "Thuban-centered circle."

To make this argument more clear, it is important to understand the concept of the pole star.  The rotation of the earth causes the heavens to appear to rotate, to an observer located anywhere on our planet.  The rotation of the heavens is most noticeable at night, because at that time the stars are visible.  The heavens appear to rotate around the celestial poles, north and south.  

This is easy enough to visualize if you imagine yourself lying on your back and gazing up at the stars at either the north pole or the south pole -- the stars would appear to turn about a point straight up.  A star located at the exact celestial north pole or celestial south pole would not appear to move, but all the others would rotate around the center point, each making a circle -- the circle's size would be based on its distance from the central point (all of these heavenly mechanics are explained in much greater detail in the Mathisen Corollary book, with numerous diagrams, and more briefly in various blog posts including this one and this one).  

Currently, there is a star at the celestial north pole (but no star right at the celestial south pole).  The star at the celestial north pole is Polaris, at the end of the handle of the Little Dipper (the "pointers" of the Big Dipper lead you right to it).  However, due to the phenomenon of precession (also explained in great detail in the Mathisen Corollary book with numerous diagrams), the north pole does not always point to the same spot in the heavens, but traces out a "circle" over a period exceeding 25,000 years (nearly 26,000 years at its current rate).  As the diagram below illustrates, precession causes the part of the sky around which everything else turns to shift with the passage of thousands of years.  While Polaris is conveniently located at the celestial north pole today, thousands of years ago Thuban in the constellation Draco marked the celestial north pole instead, and Polaris and all the other stars made circles around Thuban:

Thus, Ross Hamilton's assertion: if the designers of the Serpent Mound intended it to represent Draco, and if they intentionally suggested, using the dimensions of their mound, a circle with α-Draconis aka Thuban at its center, then they may well have been trying to imply that Thuban was at the center of the circling skies -- and thus to imply a representation of the skies in the epoch just this side of 3000 BC!

This assertion, of course, is very much at odds with the conventional assertion that the Serpent Mound (and the other mounds of the central US) were built by the Adena and Hopewell cultures, or perhaps the Fort Ancient culture, which were Native American cultures active in the region between 1000 BC and AD 1750.  
Based on the dating of Adena burial mounds constructed not far from the Serpent Mound (some are marked as yellow hexagons in the green Serpent Mound map shown above), the Serpent Mound was originally assumed to have been contemporary with these burial mounds and dated to about AD 1200.  Later researchers found ash in the soil beneath the surface of the mound, which they could carbon date, arriving at an earlier date of AD 1070 on two of the samples.  However, one sample turned up a reading of nearly 3000 years ago (around 1000 BC).  This is still too late for Thuban to have been the pole star, however, as the diagram above illustrates.  So the assertion that the mound references a knowledge of Thuban as the pole star is controversial indeed.
By the way, even many conventional archaeologists will admit that the Great Pyramid of Giza in Egypt incorporates pointers to Thuban, which was the pole star when most believe that the Giza pyramids were constructed.  As I have already pointed out in the Mathisen Corollary book and in other blog posts, the fact that the Great Pyramid is still aligned to true north and that its shafts and passages are still aligned to significant and identifiable stars shows that the conventional geological theory of plate tectonics may be seriously flawed.  The Giza pyramids, and other ancient sites with intact alignments such as Newgrange and the megalithic temples of Malta, are all acknowledged to date to many thousands of years BC.  

If the Serpent Mound incorporates a clear line pointing to true north (as Ross Hamilton demonstrates that it does) and even if it only dates to 1000 BC (as one radiocarbon dating suggests that it might), this intact alignment would seem to add to the evidence that the continents are not drifting around the way that tectonics says they are, and yet another reason why I believe that the hydroplate theory of Dr. Walt Brown explains the evidence we find on the planet around us better than the tectonic theory does.

Of course, drawing a circle around a point alleged to be Thuban, and doing it in such a way that it touches the front and rear of the Serpent Mound, does not ipso facto prove that the mound was built during the epoch in which Thuban was pole star.  However, the fact that it is possible to do appears significant -- it could be coincidence, but it is also true that had the mound not been constructed so symmetrically about this "Thuban point" then any circle with the Thuban-point at its center would have "cut off" a portion of the construction on one end of the snake or the other. 

If the existence of such a circle does indicate a desire to memorialize the era during which Thuban was pole star, one could still argue that the mound was designed and built hundreds or thousands of years later as a commemoration of that time period, and not during that actual time.  However, this would imply an understanding of the phenomenon of precession -- a very subtle phenomenon that is not easy to identify, because it moves the sky by only one degree every 71.6 years.  Precession is so subtle that conventional historians believe it was only first discovered by the Greek astronomer Hipparchus around 150 BC (see discussion in this previous post).  

While I believe it is very clear that ancient civilizations understood precession to a degree that was even more precise than that determined by Hipparchus, the fact remains that to perceive precession requires the ability to measure the location of stars, a method of recording those locations, and written records to pass those observations down to subsequent generations of observers, because one human lifetime is not enough to see a change.  It also requires analysis of those records, and then it requires the formulation of a theory about what is going on.  

Thus, if the Great Serpent Mound incorporates such information, it implies astronomical observation and written records stretching back for hundreds of years before it was ever designed and constructed.  Based on the fact that very few Native American cultures developed written forms of communication, the idea that the Great Serpent Mound could have been built later as a commemoration of an earlier precessional age is anathema to conventional anthropology, and thus the assertion of Ross Hamilton that it depicts Thuban as pole star is unacceptable to conventional theorists on two counts -- first because it would imply that it may have actually been designed when Thuban was pole star, which is well before conventional anthropologists want to admit, and second because if it was designed later but refers to a time when Thuban was the pole star, this would imply understanding of precession perhaps before Hipparchus and among cultures that would not be expected to understand precession, a subtle phenomenon which requires precise measurements and written records to notice.

There is one other startling aspect of the Serpent Mound which could throw some further light on this subject, and one which I do not believe has been observed previously*.  Notice in the diagram above of the northern circumpolar sky that the center of the great circle caused by precession falls within the largest coil of the constellation of the great serpent Draco (the hub-point towards which all the red meridian lines converge in the diagram).  Now, take another look at the diagrams of Ross Hamilton which superimpose the stars of Draco with the contours of the Great Serpent Mound of Ohio (perhaps easiest to see here).  

What is absolutely remarkable is the fact that the spiral tail of the Great Serpent Mound does not correspond to the quadrilateral of stars that we usually think of as the "head" of Draco (Ross Hamilton does point out that the head of the Great Serpent Mound is at the other end of the constellation from the end that we usually think of as the "head" of Draco today, and notes that the ancients may well have seen the other end as the head, not least because the name Thuban apparently might mean "Serpent's Head"). 
However, he does not point out* that this spiral tail of the Serpent Mound actually falls within that very same dramatic "hairpin" turn of the constellation Draco where the center of the Great Circle of Precession also falls!  In other words, if the Serpent Mound really does correspond to the constellation Draco, then it is very possible that this coil represents the hub of the circle of precession!

This is an astonishing possibility indeed.  It would represent an unmistakeable message from thousands of years ago of an awareness of precession, and not just an awareness but a sophisticated understanding of precession and its long-term effect on the heavens -- to know the center of the precessional circle requires non-trivial records over periods long enough to determine the motion of the heavens.  In other words, noticing one degree of motion is not really enough to determine all three hundred sixty degrees and to determine where the center of that circle should be.  If they knew where the center was, and indicated it by the coiling tail, then it is an absolutely astounding revelation from the past.

Note that the coiling tail would be a very apt design to imply spiraling motion.  Also note that the direction of the tail's coil implies a serpent emerging from the center-point of the coil and proceeding in a counter-clockwise direction -- the same direction that the celestial north pole moves around the center of the precessional ring.

Finally, note that if the coiled tail really does indicate the center of the precessional circle, then it very much confirms the possibility suggested by Ross Hamilton, that the Serpent Mound represents knowledge of a time when Thuban was pole star -- either because it was pole star when the mound was designed, or because the designers knew about precession and were able to hearken back to a time when Thuban was pole star.  In other words, if the Serpent Mound incorporates knowledge of the hub of the precessional circle, then this supports assertions that the mound incorporates a representation of the hub of the other sky circle, the celestial north pole.
Who on earth might have been responsible for this incredible ancient monument?

* Later note: it has come to my attention that Ross Hamilton has also previously noticed the correspondence of the spiral tail of the serpent with the hub of the circle of precession, and has published diagrams to that effect in Wonders and Mysteries of the Serpent Mound, available in the Serpent Mound museum store at the site itself.  This only strengthens the assertions made above -- these correspondences are amazing to contemplate!