Allegheny County — the county Pittsburgh’s in — is named after the Allegheny River, the river of the Alleghans. But who were the Alleghans? An Indian tribe, right? Well, yes and no.

The Alleghans or Allegewi were described in the oral history of the Delaware tribe as a race of tall and strong people who lived in great fortified cities and built enormous sacred mounds. When the distant ancestors of the Delaware migrated westward across Ohio and Pennsylvania they were refused passage by these well made giants, and a bloody, bitter war began, a protracted struggle that ended only with the destruction of the Allegewi.

Naturally, Americans of the nineteenth century were quite taken by this story, and when the remaining mounds were excavated and found to contain oversized bones, cryptic inscriptions and sophisticated artifacts, they were quick to embrace and honor the noble, doomed Allegewi, some even seeing them as a lost tribe of Israel or refugees from Atlantis.

But archeologists of our day are more comfortable with myths as fiction. The colossal skeletons in the mounds crumbled to dust when exposed, and the Allegewi have similarly disappeared in the glare of modern inquiry. Today it’s generally thought in academic circles that, not only do the Allegewi no longer exist, they have in fact never existed. The mounds, a few of which still remain, were built by two sort of co-existing "cultures," the Adena and the Hopewell. The Adena, who do seem taller than the norm and have no direct genetic connection with any existing Native American tribe, did construct a large, now destroyed mound in Pittsburgh. Their most notable remaining creation is, of course, the Great Serpent Mound of Ohio, a quarter mile long earthenwork serpent, portrayed with its jaws closing around a smaller oval mound.

But being named after an imaginary, non-Indian tribe — doesn’t that sort of weaken the authority of the judges and lawyers in the Allegheny County courthouse with the name chiseled on the side — or all the cops with Allegheny County engraved on their badges? Evidently not.

The other thing is that whatever you want to call them, Allegewi, Atlantean, Hopewell or Adena, the society of the mound builders itself disintegrated so precipitously that their successors couldn’t recognize their monuments or imagine people like themselves building them. That’s the story of ancient America, isn’t it, lost cities and vanished civilizations, the sudden accelerations and crashes of culture, great capitols and empires collapsing at their apparent peak — the Olmec, Maya, Teopithuacan, Mississipian, even the mighty Aztec fell over like a house of cards.

I’ve read a lot of explanations about these repeated urges to "abandon and destroy" their cities, the pulp paperback theories as tenable as the university press ones, none of them remotely provable. Despite many firmly differing opinions, the events remain "poorly understood," the only solid fact being that this rise and fall seems to occur over and over again. Maybe we won’t know for sure until it happens to us.