community experienced a population and construction boom. Throughout the 10th century, Chacoan building techniques spread from the canyon to neighboring regions. By AD 1115 at least 70 outlying pueblos of Chacoan provenance had been built within the composing the San Juan Basin. Experts speculate the function of these compounds, some large enough to be considered great houses in their own right. Some suggest they may have been more than agricultural communities, perhaps functioning as trading posts or ceremonial sites. Thirty such outliers spread across are connected to the central canyon and to one another by an enigmatic web of six Chacoan road systems. Extending up to in generally straight routes, they appear to have been extensively surveyed and engineered. Their depressed and scraped caliche beds reach wide; earthen berms or rocks, at times composing low walls, delimit their edges. When necessary, the roads deploy steep stone stairways and rock ramps to surmount cliffs and other obstacles. Although their purpose may never be certain, archaeologist Harold Gladwin noted that nearby Navajo believe that the Anasazi built the roads to transport timber; archaeologist Neil Judd offered a similar hypothesis. Archaeoastronomy Sun Dagger Two whorl-shaped etchings near the top of Fajada Butte compose what is called the "Sun Dagger" petroglyph that is tucked behind the eponymous rock panels of the "Three-Slab Site". They are symbolically focal. It consists of two spirals—one principal and one ancillary. The latter left-hand spiral captured both spring and fall equinoxes; its artifice was revealed by a descending spear of light, filtered through the slabs, that shone upon it and split it in two. The former and larger whorl to its right was lit by the titular "sun dagger", which bisected it through another interplay of slab and sunlight. Light struck it, brilliantly, as the summer sun attains its solstice midday peak. The Chacoans were said to be marking, as artist, "Sun Dagger" discoverer, and leading proponent Anna Sofaer puts it, "the middle of time". Each turn of the 9.25-turn large spiral was found to mark one year in the 18.6-year "lunar excursion cycle" of the rising mid-winter full moon. This record is kept by a slab-cast lunar shadow whose edge strikes in succession each ring. As the full "minimum moon" closest to the winter solstice rises, the shadow's edge precisely strikes the center of the larger spiral; it steps outward year by year, ring by ring, until it