Chaco is two things at once: an archaeological problem of the first rank, and a live political fight over the ground it stands on.
What the Chacoans built. Between about 850 and 1150 a society centred on this dry canyon raised great houses of coursed sandstone, some rising to five storeys and holding hundreds of rooms, and laid out wide, straight roads running for tens of kilometres to outlying "great house" communities across the San Juan basin. Several buildings encode astronomy: walls and windows aligned to the solstices, and to the 18.6-year cycle of the moon's standstills. This was a planned centre coordinating a region, not a single town.
What became of them. In the twelfth century the system contracted and the population moved north and then south, to the mesas and river valleys where the Pueblo nations live today. Chaco is ancestral to them in a direct and stated sense; it is not a ruin of strangers.
The fight now. In June 2023 the Department of the Interior withdrew federal land within roughly ten miles of the park from new oil and gas leasing for twenty years, a protection Pueblo nations had sought for decades. The Navajo Nation objected, because Navajo allottees hold land inside the buffer and draw royalty income from it, a genuine split between tribal governments, not a simple story of natives versus industry. In 2026 the Bureau of Land Management moved to rescind the withdrawal on a two-week comment window, and Pueblo leaders opposed both the substance and the haste. The atlas records the positions and the parties, and does not decide between them.