MANKATO — It’s perhaps one of Blue Earth County’s most romantic legends. 

Pierre Charles Le Sueur, accomplished diplomat, explorer and trader, jumps out of the roughly hewed longboat and wades through the crystal clear waters of the Blue Earth River.

Above him, amid the oaks, looms a wooden palisade, concealing among other things a collection of scaffolding and log cabins. A thin column of smoke rises above the canopy of trees, signaling the encampment’s existence.

Fort L’Hullier: its existence is more than just legend or folklore. (Though at times, it resembles smoke.) It’s an epic mystery, so grand it has inspired nearly three centuries of explorers to search for its remains. Today, of course, this region is officially part of South Bend Township, or what area residents refer to as “LeHillier,” a quiet burg just beyond the city limits of Mankato, and across Highway 169 from Land of Memories Park.

The newest explorers and searchers for Fort L’Hullier are a group of students from St. Mary’s University in Winona, according to a press release.

“I’m just hoping that we’ll find something good,” associate professor John Ebert said.

Last summer, master’s students in Saint Mary’s geographic information science program researched the fort’s location for about a week. This summer, with a $8,800 grant from the Minnesota Historical Society, they’ll validate and expand upon their previous investigation, examining historical oral accounts and written documents for spatial clues to the fort’s location.

“We plan to bring some newer technology to this project,” Ebert said. “We will go through historic documents to find any special components that provide tangible mapping clues such as unique elevations or descriptive accounts detailing the fort’s location, such as ‘southern exposure located on the west side of the Blue Earth River near an inner bank corner.’ If we can effectively correlate as many of these clues (as possible) together in one location, it will give us the best information to determine where to conduct new site visits for archaeological digs.”

Once the students identify potential locations for the site, archaeologists will begin field investigations, perhaps even as soon as mid-fall. Bear Creek Archaeology of Cresco, Iowa, is assisting with the project.

Ebert said the likelihood of finding the fort depends on a variety of conditions. For example, flooding may have erased evidence of the fort or the site could now be a developed subdivision or industrial area where limited or no digging is possible.

Not only that, but historic documents that reference the fort contain contradictory descriptions of its location. The measurements used are now archaic, and the geography of the area has changed.

“Some say it was east of the river and others say it was west of the river,” Ebert said. “A half-league 300 years ago is different that a half league today.”

Hannah Hutchins, one of Ebert’s students, says the class wants to find a concrete area for archaeologists to dig by mid-August. A 2008 Mankato East High School graduate, she said the project has helped her start to really appreciate Mankato’s past.

She wants to find the fort because she thinks it is of cultural and historical relevance to the city. Mankato has a lot of history people don’t know about, she said. Maybe the fort’s discovery could bring some of it to the forefront.

The success of the project will depend not only on how many spatial clues the students can dig up, but how accurate they are.

“The thing with historical GIS is just finding the data,” she said. “Because that’s the foundation for your project. If you don’t have data, you can’t speculate anything.”

Ebert thinks they may have enough. On the other hand, they may not.

“We could find it,” he said. “We could find nothing at all. Or we could find evidence that leads to further investigation. I’m hoping for anything except that we do not find anything.

“It’s not a needle in a haystack, it’s a calculated needle in a haystack,” Ebert said. “But I’m hopeful.”

Thomas Hughes was dead certain. He had found Fort L’Hullier and nobody could convince him otherwise. A large monument, which is today located near the intersection of highways 66 and 90 near Mount Kato, is a testament to just how sure he was.

Weren’t the 17 headless skeletons proof enough?

Found near a trail that skirted the foot of a large hill near the mouth of the Blue Earth River, they undoubtedly belonged to a group of Sioux Indians, the Mankato lawyer announced upon their discovery in 1907.

The French fort, located upon the hill itself, was likely abandoned as a response to Native American hostilities, Hughes theorized. That was in 1702, just two years after Le Sueur discovered what he thought were outcrops of non-metallic copper along the Blue Earth River and established a fort there so he could mine it.

Later he’d discover the “ore” was actually green and blue clay. When he returned to the fort after attempting to sell the substance, he found it attacked and abandoned.

Its location was quickly forgotten, with any attempt to find the fort — Hughes’ included — unsuccessful.

Archaeological studies later proved the amateur historian wrong.

Still, “Hughes is one of my idols,” retired Gustavus Adolphus College geography Professor Robert Douglas said. “He was convinced the fort was up there.”

Hughes’ legacy, if slightly dubious, launched Douglas on a search of his own for the fort in 1999.

Flash back several years ago. Douglas ground to a stop, got out of the car and stepped out onto the hard, gravel surface of a mammoth rock quarry.

In the passenger’s seat, his wife sat holding the GPS.

Was this it? A years-long search had culminated in this?

Before Douglas got out of the car, he had been excited beyond belief. Now he just felt resigned.

He had been looking for the Fort L’Hulier mine, but all he found was stones and dust.

“Oh well,” he finally said. To anyone else looking for the fort or the mine, “I wish them all the luck.”

Luck indeed. Douglas had stumbled across a clue Hutchins says could just help.

Long before either Hughes or Douglas began searching for the fort, Jean-Nicolas Nicollet, a french explorer and negotiator, did the same, Douglas said.

While doing research, Douglas found a series of latitudinal and longitudinal coordinates recorded by Nicolet while he was surveying the area. Before traveling from St. Peter to South Dakota, Nicolet went in search of Le Sueur’s rumored copper mine — he wrote down coordinates for a site he thought might be it.

Nearly 200 years later, those same coordinates landed Douglas in the middle of a stone quarry near the Blue Earth River.

“Wow!” Hutchins said. Even if the extra data point doesn’t help, Douglas’ search is just another example of how modern-day technology can be used within historical contexts.