Elvis was found in remarkable condition, for a man who had spent a century underground.

The corpse’s real name was never learned, but the sewer workers who happened upon his unmarked grave in March 1989 nicknamed the man for his groomed handlebar mustache and button-up sweater.

The workers were laying pipe behind a condo development at the corner of Belle Plaine and Neenah avenues, a residential addition to the Dunning Square strip mall built a few years prior. It wasn’t until after the contractors reported Elvis to police that they learned he lay alongside as many as 40,000 poor, indigent and infirmed Cook County residents, all decomposing underneath the neighborhood now called Dunning.

“Nowhere else in the country has a cemetery with hundreds or thousands of graves been so nearly forgotten that a developer had to rediscover it by accident,” wrote Harold Henderson in a September 1989 issue of the Chicago Reader.

For the first time in decades, crews are again moving dirt where the Cook County Poor Farm and Insane Asylum accepted patients between 1855 and 1912. But this time, builders are determined not to hit any surprises.

Chicago Public Schools demographics director Jim Dispensa flashed renderings last October of the $70 million high school, which the district began planning as far back as 2003.

The three-story brick building would accommodate about 1,100 students, opening space at the severely overcrowded Taft High School in nearby Norwood Park. Plans sit the school behind a new turf football field and running track, which would abut Irving Park Road just east of Oak Park Avenue. Another slice of land to the northwest will be set aside for development by the Chicago Park District.

During the presentation, Dispensa noted the city had accounted for “archeological concerns” that had been raised during planning.

Those concerns date back to 1851, when the Cook County board bought 80 acres of farmland about 10 miles northwest of the nascent city of Chicago, building a three-story “poor-house” where the city’s destitute could come live while simultaneously working the land.

The county added an insane asylum to the grounds, and by the 1860s, workers began burying dead patients behind the facility. A railroad line was built to shepherd the city’s homeless and disturbed up to Dunning. Locals called it the “insane train.”

“That’s how they dealt with people who were living on the streets in those days,” according to Barry Fleig, a genealogist and cemetery researcher who began investigating the site after the 1989 find. “If you were homeless or sick and didn’t have anyone to care for you, you were sent to the farm.”

Records show that by 1890, the county was burying about a thousand bodies on the grounds each year, according to Feig. When they ran out of space east of the railroad — now Normandy Avenue — they opened a new cemetery site just west of Oak Park Avenue. Feig calls this site the “new grounds.”

In 1912, the county sold the entire plot of land to the state, who stopped keeping burial records. The campus became Chicago State Hospital, which now survives as the Chicago-Read Mental Hospital.

After Elvis emerged in 1989, Fleig began poring through old county records and interviewing longtime residents. He floored developers and local officials later that year, when he determined that no fewer than 38,000 bodies lay beneath the Dunning grounds.

Sure enough, as the condo development pushed forward, more corpses turned up. Excavators found 115 bodies while digging foundation for a new home in 1990, grinding the project to a halt.

But seven months later, the Chicago Plan Commission allowed the developer to move the bodies to the original cemetery site, just went of Neenah Avenue, and finish its planned work. The site is now Read-Dunning Memorial Park, an acre-sized clearing marked by chipped stone tablets recognizing the dead.

Around the same time, newspapers began reporting proposals to build a school in the clearing east of Oak Park Avenue, which had been productive farmland as late as the 1960s. Ironically, this tract — one of the only spots to remain undeveloped until this year — is the only section of the vast property where Fleig is nearly certain no bodies are buried.

The city purchased the land in 2010 and began sketching plans for a new school.

It was immediately clear they’d have to be on the lookout for human remains. In 2015, state workers had to reroute a resurfacing of Oak Park Avenue when they hit bones during excavation. Fleig, of course, had warned them months earlier that they’d run into bodies.

The city’s Public Building Commission dug trenches through the site of the school, studied archeologists’ maps and used radar technology to search for human remains, according to spokesman Bryant Payne. They also drew up a five-page list of “archaeological protocols,” instructing workers remove and relocate any remains they find.

“Contractor shall...remove all coffin hardware and associated grave artifacts” and “place in plastic storage containers all human skeletal materials,” the document reads. Once the remains are set aside, the builder would have to coordinate with state preservation agencies to find a final resting place for them.

It’s a precaution that may prove necessary, Fleig said.

“The bad news for the school project is that we’ve found remains scattered all over these 320 acres,” Fleig said. “There are some pockets of burials that I’ve mapped, that I don’t understand why they’re there.”

One such discovery was documented in November 1989, when the student newspaper at Wright City College reported a skull and femur bones found during construction of an engineering building at the southwest edge of the campus.

And one of the maps in Fleig’s possession, drawn up by a former administrator of the mental hospital, marks skulls that were found on the site of a youth wing of Chicago State Hospital. The area is now being excavated to make way for the high school’s football field.

“This whole area went through several phases of building... so a lot of debris and bones may have made their way out of the old grounds,” Fleig said. “And just because certain areas were marked as cemeteries at the time, it doesn’t mean some people didn’t get a little sloppy.”