Down Arapahoe street, the military had blocked off the corner with the 16th Street Mall. Denver central, Saturday morning, with three black Jeeps pulled up and big men in black pulling on bullet-proof vests. This looked heavy. So did the men. Morbidly obese, two of them, beyond the standards of an American police force, full tattoos reaching out of their collars and up their faces. Still, the guns in their hands, full magazine automatics were … plastic. They were unmistakably plastic. Another unit was setting up on the other corner. They all had “Umbrella Corp” emblazoned across the chest. Between the two groups, among the shoppers, the bloodstained, the mangled, the mutant, shuffled towards the park. Real cops watched the fake cops, and the homeless shuffled among the shufflers. You have to hand it to Denver, when they put on a zombie crawl they really make an effort.

This was the ninth of Denver’s zombie crawls — a day, for the uninitiated, when thousands of people dress as various figures of the undead and shuffle down the main street — something that’s become a feature of the Mile-High City. The ritual, initially a bust-out activity of gamers’ conventions, appears to have started around the late ’90s (various places from Milwaukee to Portland lay claim to being the first), and it has subsequently spread to the world. But nowhere has it been taken up more enthusiastically than in the United States, and few places are as serious about it as Denver. Run by the Denver Film Society, the DZC has broken the world zombie crawl record once, and was going for the record again today. Since there is no distinct march — the crawlers shambled among the general populace, and considerably outnumbered them — cameras linked to face recognition software were being used to count the marchers and screen out double counting.

Why would Denver, of all places, be home to the largest zombie crawl on the planet? The Mile-High City has come a long way from being the midwest centre with a slightly hip fringe of 20 or so years ago. With expanding IT, advanced manufacturing and R&D, cheap rents, and the snow an hour’s drive away, the place is now a key new class outpost, and they have transformed its culture in their own image, reinvigorating rundown inner-city areas, rebranding the place. Half the people of that stripe in Denver came for a college degree and never left, as they might have done a decade ago. But now, New York, LA, and the Bay Area are priced out — and with the world gone online, it matters a lot less where you are. Life becomes a lot more about a neighbourhood than a city, about reinhabiting where you are.

With that substantial cultural shift comes an appetite for the carnivalesque, the aleatoric, the ironic. San Francisco was the first of such cities, and you could pretty much map the spread of American hip as a virus spread from San Francisco Bay. From Santa rampages to makerspaces, stripperoake to burlesque black masses, most of it came from San Francisco first — and then hit the ground running as the city became a buttoned-down tech dead zone. Had such diversions remained the preserve of the new class who spawned them — the world depicted in The Big Bang Theory –– they would be a minor diversion. But as old cultures died away, worlds of class and congregation, their place has come to be taken by these new, more ironic forms of coming together. Zombie crawls, comic cons, gorilla rampages for charity — in America, they have replaced the civic city parades, the marching girls and flowered floats of innumerable newsreels they once satirised. The old celebrations were focused on local stories, heavily censored, of pioneer treks and industrial development, of societies that produce themselves. Zombie crawls come from an era when consumption defines our identity; they’re folkways of popular culture, a way of bringing its all-encompassing flux under control. It’s also a way of re-enchanting life, and the body, in an era when both production and consumption have been flattened out.

“This determination to insert the fantasy into the real — is it a response to a real that seems to many to be impervious to transformation?”

The zombie walkers only shambled on a circuit of three blocks’ length, but they passed three Starbuckses when they did. The tech city down at the south end of Denver will supply more than its fair share of zombie walkers, and it’s a chilling series of high-tech warehouses for endless screen work. Zombies have been a part of American popular culture for more than a century, but under different guises, first as an expression of racial fears and obsessions, then in the ’60s and ’70s, of nuclear apocalypse and out-of-control science. But it has only been in the last decade or so that the sub-genre has become obsessional, all-encompassing. Zombies are now caused by viruses, by mutation, by war, by science gone wrong, or simply by the coming of night.

The original zombie crawls had the zombies bursting out of theatres where horror movie marathons were playing  — and Colorado, home of the Telluride horror film festival, seems to have a heavy-hitting horror contingent — to genuinely freak people out. They were a way of extending the movies — usually shot with available lighting in city streets — into those streets themselves, a sort of happening. They were also a way of dealing with an aspect of the genre particular to its consumption in America, that the streets are full of zombies. They’re called the homeless. In Denver, they congregate in the 16th Street Mall, where the crawl took place, and being the kind, liberal city that it is, it does not disperse them (cities have been known to ship their homeless across the county line; Arizona has been known to ship them across the national border). Many are simply people down on their luck, but even the most focused and cognisant have a manner different to the self-enclosed way that Americans move through streets. They tend to be thinner, pallid, more lined, rougher round the edges, especially if they’ve got a crack/ice/insert new drug here habit. And of course a good 30% of them are stark staring mad. People move around the homeless, keeping a watch on them from the corner of one eye, while the homeless simply live on the street — laughing, chatting, dealing, arguing, fighting. The two groups for the most part, glide between each other, in separate spaces. So the zombie craze is in part a masquerade of American life, a place to put all the angst and guilt of living this way — and the fear that one might pass from one side to the other.

But what was most remarkable about the Denver zombie crawl was the way in which the celebration itself had mutated. Purists are known to despair at what it has become, a vast cosplay event in which the myth-kitty of traditional and popular culture is raided for images that can then be horror-fied. But once let go, the creativity is stunning — zombie Santas with their own antlers, cannibal Peter Pans, Ebola nurses, and a feral Where’s Wally pack — and not a little alarming.

The city loves the zombie crawl and rerouted the entire public transport system to accommodate it. But there is something very strange about a giant cosplay event — in a country with open carry laws on guns — in which dozens and dozens of men and women dress up as paramilitaries from the Resident Evil franchise and commandeer strategic cross-points in the city, complete with black Jeeps. It’s a very Mad May, when men dressed as zombies can chase young girls through the street, howling with hunger.

It’s fantastic, a product of a feature of American life very different from the Australian — the ceaseless determination to bud off new festivals, celebrations, insta-traditions, something going back to Thanksgiving itself. But this determination to insert the fantasy into the real — is it a response to a real that seems to many to be impervious to transformation? What relationship is there between a pop culture celebration into which people pour all their living energy and a political process that appears to be a walk of the living dead? What strange world is it where I had to mock-talk my way past a security checkpoint run by fat postgrads in black rubber, while real cops looked on? Strange days in the Mile-High City …