High school teacher and archaeologist Chip Clatto stands six feet below ground level in the basement of a demolished 19th-century home on this city's south side.
With excavated earth piled around him, he lifts a sheet of plywood at his feet and reveals a brick-lined, manhole-sized tunnel entrance - and what may be a portal to one of the most storied chapters in American history: the underground railroad.
"I'm guessing the tunnel went 30 feet to the southwest, where it connected with Cherokee Cave, which led out to the Mississippi River," says Mr. Clatto. "Once the runaway slaves crossed the river, they were in a free state [Illinois]."
Despite a flurry of legislation in the 1990s aimed at preserving the remnants of safehouses and routes that ferried slaves to freedom, many possible sites are facing destruction. The Lemp Avenue tunnel presents a cautionary tale of what happens when historic derring-do collides with the forces of modern politics and urban redevelopment.
It is also a compelling detective story, which begins with a curious professor who lives three houses away from the dig. For years, Mark Sarich had heard tales about a neighborhood house that reportedly had been a depot on the underground railroad.
Mr. Sarich had always dismissed the stories, doubting that an oral tradition could carry over 150 years, given the dramatic shifts in neighborhood demographics. But in 1998, he uncovered telltale evidence of an underground-railroad connection.
Looking through historical records, he located maps from the 1850s that showed the house bordered on a commons with two cemeteries and two churches, one of which was German. Stations on the underground railroad were often located near graveyards, which served as both navigational aids and hiding places. And Germans were often fervent abolitionists who were known to aid runaway slaves.
Sarich also became aware of confirmed underground-railroad safehouses in what are now St. Louis suburbs, eight miles due west - from whence the Lemp Avenue site is in direct line with the Mississippi River.
He took his findings to a city official, who brought in Clatto in March 1999. By examining the house's oven-fired bricks and hand-hewn beams, Clatto quickly became satisfied that the house dated back to the 1840s.
But the city deemed the link to the underground railroad circumstantial and ruled the house was in dangerous disrepair, demolishing it in April 1999.
Nevertheless, Clatto got a permit to excavate the site. Two months ago, an artifact was found that electrified the high school crew he directs.
It was a cowrie shell, a small seashell carried as a symbol of a slave's African roots, formerly used as currency. The next day, a pinkie-sized bone carving of an elephant's trunk was unearthed. If German habitation on the site in the 1850s can be further confirmed, then such slave artifacts at the scene would be considered a strong indicator of underground-railroad activity.
Two weeks ago, Clatto located the long-rumored tunnel entrance under mounds of debris in a corner of the basement. It is lined vertically with bricks - a technique noted elsewhere in the few cases where the underground railroad actually went underground - but Clatto was even more excited by what he found when he began digging out the tunnel.
Immediately below the entrance, a shallow room opens up into a squat dome. It is plaster-lined and can hold four prone people.
The city has extended Clatto's archaeological permit for only another month and he fears that the site could soon be turned into an asphalt parking lot.
Indeed, the likelihood of absolutely confirming the site as a stop on the underground railroad - through discovery of a diary in the tunnel, for instance - is remote.
Yet Clatto believes that, if granted 90 days to dig out the tunnel, the crew might find etchings or drawings in the plaster-lined dome or limestone below, markings unique to the underground railroad, or African or slave culture. Either would come close to smoking-gun evidence.
Although the National Park Service appears hesitant to entangle itself in local disputes over unconfirmed underground-railroad sites, Clatto and Sarich hope the NPS will eventually acquire the property and rebuild the house with its original bricks, many of which remain on-site.
"Imagine a total reconstruction, where you walk in and suddenly you're in a different world - a stop on the underground railroad," says Sarich. "You would actually crawl into the tunnel and they'd close the door on you, and you could feel what it was like to be a runaway slave. This is where people put their lives on the line for freedom. We need to enshrine places like this."
(c) Copyright 2000. The Christian Science Publishing Society