Rectangle Mound


My son William standing on the rectangular mound sometime in the late 1990s.

Discovery and Location

Sometime in the 1990s, while looking for noxious weeds in the pasture on the Wright Place, I stepped down and then up.  After a couple more steps I stepped down again.  This seemed unusual, so having a corn knife with me, I cleared the chest-high brome grass, revealing a low-relief rectangular mound.  This mound is located on the east edge of the terrace (higher ground) above the nearby O’Neill Valley Creek bottom and is a few hundred feet straight east of a large mound located in the center of this bottom.  There’s a sharp cut in the terrace bank leading down to the bottom near the southwest edged of the mound, suggesting that perhaps people walked up and down there on their way to or from the large mound to the west.

Me standing near the bottom of the cut with the flagged rectangle on the edge of the high bank behind me.


All four corners of this mound are rounded, and it is slightly higher and extends slightly farther to the south in its southwest corner.  Over all, though, it is an unmistakable rectangle and when I first saw it, it reminded me of an altar. (This mound may in fact be an altar – though not this large, Pawnee earthlodges all had a raised rectangular altar on their west end – a buffalo skull with a rectangle painted on it in red rested on this altar, and if the residents had one, a sacred bundle hung above it.  The rectangular shape and location in the west symbolized the Garden of the Evening Star, the Pawnee source of both animal and vegetable life.)

Like the two ovals on top the large mound to the west, this rectangle rises only a matter of inches and has a shallow “trough” around it.  This shallow area is only a couple of feet wide on the east, south and west sides, but extended several feet farther to the north, forming a semi-circular depression.

Outline of large depression north of the rectangle.

A small berm of slightly raised soil surrounds this trough, suggesting that dirt dug from the trough was deposited on both sides of it – on the mound and on the outside edge of the trough.  An attempt to insert a soil probe in the trough proved impossible – the ground is extremely compacted.  The ground outside the trough, however, is not, suggesting perhaps that this track may have been walked and/or danced on during ceremonies.

Adjacent Mounds

There are at least two other long, narrow mounds near the rectangle, each of which changes direction at some point.  The west end of one of these mounds lies a short distance from the southeast corner of the rectangle (there seems to be a depression running some distance south to another cut in the terrace that may have been used for drainage) and runs east-southeast for a distance before curving to run straight east.

The south end of the other mound lies east of the northeast corner of the rectangle and runs north-northeast for a ways before angling due north.  Both of these mounds are very low relief (less than the rectangle) and have numerous disturbances in them which dowsing indicates may be burials.

Uncompensated drone photo of rectangle and two adjacent mounds. North is at the top. The long mound at the bottom is cut off on the east by plowing.  The ends of the mound to the north are indistinct.  The small brown patch to the west is water in the nearby O’Neill Valley Creek.


In examining the area around the rectangle I noticed several small depressions (old post molds?) both to the north and to the east of the rectangle.  I had no idea if they were connected to the mound, but made note of them just in case.  When we reseeded the pasture around this mound to native vegetation in 2013, I decided to record the locations of these depressions since once the prairie grass was established they would be difficult to find.

To accomplish this my family and I set four orange tent stakes in the corners of the rectangle as references to measure distances from.  Because the rectangle slopes gradually up from the surrounding trough, it is difficult to determine exactly where the borders of the rectangle are. We also didn’t know if we should mark the bottom or the top of the mound so we arbitrarily chose points near the bottom.  Once we had the stakes initially placed, we measured the distances between them, including diagonally, and adjusted their positions to make sure we had a perfect rectangle and not a parallelogram.

This enabled us to measure the centers of the depressions on the north from the stakes in the northwest and northeast corners, and on the east from the stakes in the northeast and southeast corners.  When looking at the measurements I realized that a depression approximately 40 feet to the east of the mound (labeled “G” in the image below) was equidistant from the north and south corners of the mound.  This suggested that at least this depression, and possibly all of them, were connected in some way to the rectangular mound.  A few years later my son-in-law Dan French plotted the rectangle formed by the stakes and the surrounding depressions using his father’s AutoCAD program:

Depressions D1 and E are very shallow.

There are also two distinct and one shallow depression at the north end of the north/south adjacent mound.

Drone Photography

In 2019 my son William and I flagged the lower edges of the rectangle as best as we could determine them visually and then marked both this edge and the four corner stakes with paint.  This enabled us to photograph the mound from above with a small drone (without the paint it wasn’t possible to discern the edges or the stakes from the sky).  Prior to doing so, I used a gnomon to use the sun’s shadow to determine and then paint a 20’ straight east/west line south of the rectangle.  This provided a reference for both direction and distance.

Drone photo and east/west line (south is at top).

Compensating the Image

Because the location of the drone over a mound and any pitch induced by the breeze can distort proportions in the photos it takes, we superimposed the CAD rectangle formed by the corner stakes over the drone image and then William used Photoshop to “warp” the drone image slightly so that the corner stakes in the drone photo (green dots) matched the proportions of the corner stakes in the CAD image (south is at the top):

Reference stakes shown in green. Though our stakes form a rectangle, we were a little off in our alignment to true north.

Geometric Analysis

Once we had a properly proportioned drone image, I began examining its geometric properties.  I printed the above image and resorted to “Kindergarten Technology” to estimate its north/south and east/west axes – I connected the centers of the dots with a pencil, creating a perimeter around the mound image, and then cut the image out with scissors and experimented folding it.  Because the image isn’t a perfect rectangle, I had to find the “best fit,” where opposite sides lined up as much as possible.  This allowed me to find and mark what I felt was a good approximation of the center axes.

I then scanned this image and William used Photoshop to overlay it on the initial image.  This gave us the best estimate we could make of this mound’s center point and its north/south and east/west axes:


As determined from folding, the center width of the rectangle is 21.43’ and the center length is 36.25’.  Comparing the east/west axis to the gnomon line indicates the figure is less than a degree off (clockwise) from the gnomon line, indicating the mound was very carefully aligned to the cardinal directions.

Relationship of length to width

Dividing the rectangle’s length by it’s width gives 1.69.  In the past I had estimated that this ratio of length to width might be 1.618…, an irrational proportion known in many places and often referred to as ‘The Golden Mean.’  However, the more precise estimate made possible by the drone photo is slightly closer to another irrational proportion also known to many cultures – 1.732… – the square root of 3.

As explained on the Gnomon page, the method I used to determine east and west, when carried a few steps further, produces a “Root 3” rectangle aligned to the cardinal directions:

A “root 3” rectangle produced by using a gnomon to determine the cardinal directions


In order to see how closely this root 3 rectangle corresponded to the rectangular mound, I had William use Photoshop to superimpose the root 3 diagram over the compensated dot pattern.  We included the depression dots from the CAD image and added a dashed blue line going straight east/west through depression “G”, the depression that is equidistant from the corners:

Note how closely the perimeter dots match the root 3 rectangle.  Instead of the southwest corner being extended, as I originally concluded, the southeast corner is slightly shorter.  Note also how close the dashed line matches the width axis derived from folding the image.

The length is very near 37.4′ and the width 21.6′

Could It Be Both?

It seems clear that at its widest the rectangle is a root 3 rectangle – probably because a gnomon was used to create it.  But why is the south side slanted?  As mentioned above, I initially suspected the ratio of side to length was closer to what is often called the Golden Mean – 0.618… (or 1.618…)  This is a very unique ratio because when a line is divided in this way the smaller line segment is to the longer line segment as the longer line segment is to the whole.  This proportion appears in nature in everything from the spiral of a chambered nautilus’ shell to the arrangement of seeds in the head of a sunflower.

To create a Golden Rectangle one starts with a square.  From the center of the base one draws a diagonal to one of the upper corners and then swings this distance down and a rectangle is then drawn from the resulting length:

Among the many unique properties of the resulting rectangle is that if a square the size of the length is added to it, a new Golden Rectangle is formed.

I had William overlay this shape on the image above to see if by any chance the southeast corner of the rectangle would be close to the edge of the Golden Rectangle.  Though the corners are rounded and thus difficult to determine exactly, it does appear this corner come very close to aligning with the southeast corner of the overlay.

Initial Conclusions

The rectangular mound may have been there for hundreds of years – if so, it’s suffered damage due to weather, being walked on by cattle for over a century, and maybe even being walked on by buffalo before that.  Given how these factors could have damaged its edges, I think the correspondence between the perimeter dots and the superimposed root 3 rectangle is remarkable.  I believe that the northeast, northwest and southwest corners of the rectangular mound was originally intended to have been this shape with these proportions – the natural shape/proportions that would have resulted if the builders had used a gnomon to lay the design out on the ground.

I also suspect that rather than evidence of sloppy construction, the southeast corner may have been deliberately shortened to mark the corner of a Golden Rectangle.  In effect, this rectangle may have been intended to be two rectangles in one.

Alignment With Depressions

Because there is a depression directly east of the center of the mound (“G”), I believe that at least some of the depressions north and east of the rectangle may be geometrically connected with it also, perhaps having served as marker points when it was being constructed or having been located later in accordance with the rectangle’s properties.

This brings up an intriguing possibility – if additional depressions are aligned with the mound, then it should be possible to determine not only it’s original dimensions but perhaps also the unit of measure the builders used.

Depression Alignments

Two of the depressions align very closely with the north (“F1”) and west edges (“B”) of the rectangle.  The image below shows dashed blue lines extending through them:

The center and axes are again nearly perfect when the overlying root 3 rectangle is reduced in size to fit the new dashed lines.

The perimeter marked from the drone photo is at the lowest edge of the rectangle – where its sides meet the trough surrounding it.  This new, smaller superimposed root 3 rectangle fits very close to the top of the rectangle, where the upward slope stops, with the distance between it’s edges and the perimeter dots encompassing the sloping portion of the rectangular mound’s sides.

The dimensions of this inner rectangle are very close to 32.36′ by 18.68′.

Diagonal Line

The diagonal dashed blue line (through depressions “G”, “F1” and “D2”) was added because it is very nearly a perfect 45 degree angle to north/south – east/west – the angle of the diagonal of a square aligned to the cardinal directions (there is also a depression to the north that very nearly fits on this line is well).  It seems unlikely this would be an accident.  I’m hoping that further research may reveal more geometric features involving the mounds and depressions in this area.

Relationship Between Inner And Outer Rectangles

When construction geometric shapes from the overlapping circles created by using a gnomon, a double square or Root 5 rectangle (called this because the diagonal is equal to the square root of 5) can also easily be created by connecting the tops and bottoms of the overlapping circles directly above and below the center line and equal to it in length:

Overlaying this image on the rectangle shows that on the north end and on the southwest corner the distance between inner and outer root 3 rectangles is the difference between the inner root 3 rectangle and the inner root 5 rectangle:

Notice how these inner rectangles are positioned so that while the upper end aligns with the north side of the mound, the south end seems to ‘split the difference’ between the long and short ends of the slanted south side.

Sacred Geometry

It appears that the rectangle may be a surprisingly sophisticated example of incorporating geometry into the building of a mound.  Why would this have been important?  Perhaps these various shapes – and the relationships among them – had symbolic significance to the builders.  Many sacred structures in many parts of the world incorporate “sacred geometry” in the belief that certain shapes and certain proportions enhance the sacred properties of these structures – perhaps people here once felt the same.

Astronomical Alignment

As discussed above, the sun was most likely used to determine the north/south – east/west orientation of the rectangular mound, and may well have been used to determine its proportions as well.  Whether or not using the two depressions explored above to determine the dimensions of the rectangle is correct, it’s clear that there is a depression straight east of the rectangle’s center.  If the eastern horizon were flat and a pole had stood in this depression, a person standing at the center of the rectangle looking east would have seen the sun rise behind this pole on the first day of Spring and the first day of Fall (the equinoxes).

The Use of Poles

The use of poles in rituals (or to attach scalps to) was common.  In Ceremonies of the Pawnee by James R. Murie he describes a ritual called the Four Pole Ceremony:

“According to the proper formula, the four holes are dug to receive the poles.  Then a secret ceremony is performed: Fat is taken from the bundle, made into cakes the size of each hole, and one placed in the bottom of each; then over it is sprinkled some pulverized native tobacco.  The secret knowledge is that the fat symbolizes the earth; the tobacco the people.”

So poles – and the holes they stood in – could have played a part in the rituals of the mound builders.

Offset Alignment

Since there is a ridge of hills east of the rectangle, an observer would have seen the sun rise behind this ridge.  Because the sun does not move straight up and down across the sky but instead appears to rise to the south when viewed from the northern hemisphere, the sun will have moved slightly south by the time it appears above an elevated horizon, its distance south depending on the elevation of the horizon.  Therefore on the equinoxes an observer standing on the rectangle would NOT see the sunrise directly behind a pole in the midpoint depression – the sun would instead appear slightly to the south of it.

2020 Fall Equinox sunrise. The road runs due east along the north side of the Wright Place. Note how the sun moves farther to the right (south) as it rises.


There is another depression (labeled “I” above) farther east of the midpoint depression.  The fact that this more distant depression is not exactly straight east from the rectangle/midpoint depression has bothered me since I first measured it.  But it may not be sloppy layout – if a pole were in this depression an observer at the center of the rectangle would see the sun rise in line with it on the equinoxes.

Because of the trees in the farmyard on the Wright Place it is not possible today to observe the eastern horizon from the rectangle.  It is possible, however, to estimate the horizon elevation using sophisticated mapping software.  My associate, Blake Trombley has determined the probable high point of the eastern horizon, it’s elevation, the elevation of the rectangle and the distance between them as being

East Horizon Elevation – 1,844′; Rectangle Elevation – 1,723′; Distance – 4,027′

Thus the horizon is 121′ higher than the rectangle (1,844 – 1,723 = 121).  The arctangent function of trigonometry can then be used to determine the angle of the horizon: 121’/4,027′ = 0.03;  arctan 0.03 = 1.72 degrees elevation.

Checking an astronomy program indicates that the sun would be about a degree and a quarter south of east at this elevation.  The far depression is 1.26 degrees south of east.  Though factors such as graze and atmospheric defraction can slightly alter the point where objects near the horizon appear, their effect would not significantly alter the position of the rising sun.


On a warm day before the Spring Equinox in 2020 my son William and I erected two tripods over these depressions.  We then cut tree branches in a shelter belt just east of these depressions and even knocked down the stems of last year’s prairie grasses (this area has been reseeded to native plants and grasses).  Though there are trees beyond this shelter belt, we were hoping the suns’ brightness would be visible through them.

Tripods erected over depressions as viewed from the center of the rectangle.

On the night before the equinox a near blizzard hit this area.  I attempted the next morning to reach the farm from town to observe the position of the rising sun in relation to the two markers above the depressions.  I became stuck in a snow drift and had to be pulled out the snow plow.  Hopefully there won’t be snow for the Autumnal Equinox in September and we’ll be able to find out if indeed the sun rises over the depression located slightly south of east.  The trees in the background, though, will still have their leaves, so it remains to be seen if the sunrise will be visible.

Update – the Fall Equinox sunrise was obscured by the trees.


The fact that both straight east and the rising point of the sun on the equinoxes are marked by shallow depressions suggests both that poles may have once stood in them and that the people who created the mound and depressions were particularly interested in the Spring and Fall equinoxes.  (It also suggests that – if my hypothesis regarding these depressions should be correct – that whoever made them knew the day of the equinoxes and understood where the sun was supposed to rise.  Without this knowledge they wouldn’t have known what day to align a pole placed in the farther depression with sunrise.)

Around the world many ancient earthworks, stone monuments and buildings align with the rising point of the sun, especially on the summer and winter solstices, the longest and shortest days of the year.  But many also align with the equinoxes, the days when day and night are equal in length (“equinox” means “equal night” in Latin).

An interest in the equinoxes carries symbolic associations that suggest a dualistic outlook on the world – day/night, full moon/dark moon, summer/winter, life/death, etc., and may imply a concern for the balancing of these opposites.

Though relative newcomers to this area, the Omaha Tribe divided their camp circle into north and south halves.  Certain clans belonged on one side or the other, and their responsibilities within the tribe reflected a need for maintaining a balance between opposites.  Presumably many other tribes felt this way as well –


The rectangle is a low relief earthen mound located on the terrace just to the east of the O’Neill Valley Creek on the Wright Place. It is surrounded by a depressed trough (there is a semicircular depression on the north) with a slight berm outside the trough.  The ground in this depressed area is very compacted, suggesting it may have been used for ritual processions and/or dancing.  There is a cut in the bank very near the southwest corner of the depressed trough, suggesting people may have walked up and down there, perhaps on their way to and from the larger mound there.

If the edges of the rectangle are taken as the points where its sides meet the surrounding trough, then its dimensions are 37.4′ x 21.6′.  If the edges of the rectangle are taken as the points where depressions align with it’s northern and western edges, then it’s dimensions are 32.38′ x 18.69′.

The rectangular mound is within a degree of being aligned to straight north/south – east/west and the ratio of it’s width to its length is very close to the square root of 3.  This suggests it was laid out using a gnomon.  The south side of the rectangle is not straight, however, suggesting that the shorter east side may denote the side length of a Golden Rectangle.

The rectangle mound is near at least two long, narrow adjacent mounds and has a number of shallow depressions near it on the north and east sides.  One of these depressions is directly east of the mound’s center; another is east of it’s north side and a third is north of it’s west side.  A fourth depression, farther to the east, is just slightly south of the midpoint depression.

The depressions near the mound may be the remains of post holes.  If so, to an observer standing in the center of the rectangle, one pole would have marked straight east while another, farther away, would have marked where the sun rose on the Spring and Fall equinoxes.  This suggests that the sunrise on the equinoxes was important to the builders.

The alignment of two depressions with straight east and the actual sunrise point on the equinoxes suggest that the builders were also concerned with the position of the sun (and that they most likely used the sun’s shadow to lay out the rectangle bolsters this contention).  It can be taken from this that in addition to being remarkable geometers, the people who built this mound were careful sky watchers as well.