Chimney Rock is itself over 535 million years old, and offers a 75-mile panoramic view of the surrounding landscape. It’s part of the San Juan National Forest and is surrounded by the Southern Ute Indian Reservation.
The Chaco culture that inhabited the Chimney Rock area centuries ago was hierarchical, with a priestly class overseeing the area’s inhabitants. Evidence suggests that the Great House Pueblo was first built in 1076 during a lunar standstill and expanded and finished in 1093 during another standstill.
When excavated, archaeological students found a lack of wood and other roofing materials; their hypothesis was that it had no roof and was open to the air.
If studying the stars, the advantages would be obvious.
The construction of the Great House Pueblo at the top of the ridge, close to Chimney Rock and its neighbor Companion Rock, had a large ceremonial role in the later years of Chaco presence.
During certain key ceremonies, it functioned as a hotel for visiting notables, some of whom came from as far away as Chaco Canyon in Northern New Mexico, 90 miles from Chimney Rock.
As the moon made its lunar cycle across the sky over a period of 18.6 years, it appears in a “lunar standstill” between the two rocks every 9.3 years for a period of approximately 2 years. At each end of its swing, the moon appears to pause for about three years, rising as the same point on the horizon before beginning to move back toward the opposite end of the swing.
This pause is known as a MLS.
The most recent MLS began in December of 2004 and lasted for 3 years. The next will begin in 2021.
Seen from the Great House Pueblo, the stone towers are slightly out of line with each other, framing a narrow window of sky between them. At sunset near the day of the Winter Solstice during the MLS, the full moon rises between the stone pillars, caught in this thin window of sky (see image above).
Watching the 18.6 year lunar cycle is not something one needs to keep track of the seasons. It is a cycle that is used, together with the ecliptic, to determine eclipses. Eclipses were seen as inauspicious events. In Central American civilizations, chimneys were blocked up and windows sealed off so that the offending rays may not reach in hiding inhabitants.
Chimney Rock was one of the major observatories used to monitor and predict these alignments. It would seem that Southwestern Native culture was monitoring the heavenly lights to watch for celestial warning signs.
Just like astrologers do today.