Monuments mark the rise of civilizations world-wide. The earthen mounds of Eastern North America are part of a long-standing monument tradition. In the Americas, mound construction starts at an early date, well before the pyramids of Egypt were constructed. Watson Brake in northern Louisiana, dated from 5400 to ca. 5000 BP, is one of the oldest-known, large-scale mound sites in North America. Watson Brake's dating placed mound construction in the Mississippi Valley at near 2,000 years before well-known Poverty Point, previously thought to be the earliest mound site in the United States. Watson Brake consists of an oval formation of 11 mounds from three to 25 feet tall connected by ridges to form an oval near 900 feet across. With Watson Brake's discovery and dating, pre-agricultural, pre-ceramic American societies were shown to be more complex than previously thought.

The oldest civilization in the Americas arose along the Pacific Coast of the Central Andes, where mound construction began by 5,100 years ago. Dr. Ruth Shady Solis, et.al., (2001) published new radiocarbon dating, altering views about early Andean coastal prehistory. Shady, reported dates between 2627 BCE and 2020 BCE at Caral. New research and radiocarbon dating published in Nature demonstrates that by 3100 BCE monumental buildings were found in the Supe, Fortaleza, and Pativilca valleys, not just at Caral, indicating complex societies with a network of 20 separate major residential centers creating monumental architecture and communal buildings.

Impressively large Caral, the earliest known urban center in the Americas, has a central zone containing six large pyramidal mounds surrounding a huge plaza (readily visible with Google Earth™ at -10.89125, -77.52235). The largest mound measures 60-feet high and 450-by-500 feet at the base, plus the adjoined sunken circular plaza. Patterns evident in orientations of Initial period monument complexes, with various complexes in a valley often following the alignment of the main pyramid, suggest a practice of astronomical determination of orientations and the transfer of the orientation of the larger complexes to smaller ones. This pattern indicates an early beginning for the cosmological ordering of monuments and built space by American cultures. Recent study at Buena Vista evidences an early date for Andean astronomy.

For thousands of years, North, Central, and South American monumental complexes arose and grew. The earthworks in Eastern North America represent a long chronology of cultures creating monuments. The rich record of earthen constructions equates to many thousands of years of history, spanning from Watson Brake and Poverty Point to large Adena mounds, to the Hopewell culture's florescence of geometic works, to numerous, diverse expressions, and to Monks Mound and the many mounds of Cahokia—the culmination in size of both earthen construction and settlement in prehistoric Eastern North America.

Monks Mound may have been positioned with a predetermined geodetic attribute, the latitude tangent equals 0.80 (Monks Mound's geodetic axis is the hypotenuse of a 4:5 triangle). Considering why sites may have been positioned where they're situated arose in relation to Cahokia after an author attributed Cahokia's placement to the nearby 60 degree solstice angle. The hypothesis gained acceptance uncritically and Cahokia was even termed, "The City of the Sun." While considering this idea, to quantify the temporal change in illumination angle, I assessed the geodetic properties of the Monks Mound latitude and discovered the '4/5 atan' latitude instead. I also determined the solstice angle hypothesis was not accurate.

The latitude where tangent equals precisely 0.80 is 38.65981 degrees. Today atop Monks Mound the latitude, GPS mean of four corner readings of upper terraces, equals 38.66052 degrees N. (tan = 0.800020). Given the formula for secular polar motion, I deduced the monument was positioned where latitude tangent equals precisely 0.80 around 1200 AD. This date is close to the radiocarbon date of the last constructs on the mound—the radiocarbon date and the polar motion dating agree. Current local plate motion modeling methods suggest less north-south motion. The current atan 4/5 latitude transects Woodhenge, matches the primary baseline of E-W mounds, and transects Monks Mound in front of the upper terrace (see two images following).