It was one of several forts the U.S. Army built in South Florida in the 1800s, allowing soldiers fighting the Seminole Wars to rest and regroup.

Fort Harrell was one of the more obscure outposts, wedged into a rugged swamp area, accessible mainly by boat. No great battles were waged there and no famous generals used it.

Yet three amateur explorers, led by a high school chemistry teacher, believe they have found its exact site and consider it an important historic find.

"It needs to be preserved and memorialized," said Shawn Beightol, who led the expeditions to the site in the Big Cypress Preserve in Collier County. "I'd like to see a monument placed there for the people who served in that godforsaken location 170 years ago. Their story needs to be told."

Beightol, 49, who teaches in Miami-Dade schools, said he has been hiking and kayaking in Florida's wildlands most of his life. About a year ago, while reading The Everglades: River of Grass, by Marjory Stoneman Douglas, he saw a map that showed forts around South Florida, including Fort Harrell.

"That got me hungry," he said. "I wanted to find it."

Beightol collaborated with two other avid outdoorsmen, Chris Harris, a computer engineer from Coconut Creek; and Tony Pernas, of Homestead, a U.S. National Park Service employee. Both were interested in finding the fort.

"I'd read just about every history book on the Everglades possible," said Pernas, explaining how he knew about the fort. "I'd been hunting for it for about a decade."

The three spent dozens of hours studying historic war maps, engineering surveys and old aerial photos. Then they made five forays into the Everglades this year to locate the site. On the last one, in June, Pernas spotted a clearing with post holes in limestone, used to support the foundation walls of the fort.

"Once we saw the holes, I knew we had found it," Pernas said.

Careful not to disturb the site, they marked its boundaries with yellow tape and estimated the fort structure to be about 135 feet long and 45 feet wide. There was evidence of a protected enclosure, possibly used for soldiers to take aim at intruders, and a boat landing on the nearby Big Cypress New River.

"In the back of my mind, it's 170 years old, so I thought it's quite possible there would be no signs of it," said Harris. "I honestly thought we'd never find it."

The trio now plans to have a professional survey conducted to document the fort site, about five miles south of Mile Marker 61 on the Tamiami Trail. If confirmed as Fort Harrell, it would be a significant find, said Bob Carr, a Davie archaeologist often hired to investigate ancient artifacts found at construction sites.

"Any vestige of the Seminole War period in South Florida would be significant because few sites have been preserved and not all have been found," said Carr, of the Archaeological and Historical Conservancy.

Fort Harrell was built around 1837 to provide Army soldiers a place to stock supplies and prepare for battles during the second Seminole War. The conflict started after the U.S. government planned to transport all Native Americans in Florida to reservations west of the Mississippi River.

In all, about eight smaller forts were erected in the interior of the state, while several other larger forts were built near the coasts, including Fort Lauderdale, Fort Jupiter and Fort Myers.

"The most significant forts were the bigger ones along the coast that were occupied for a longer time," Carr said. "But the interior ones were important, too."

Before the site was rediscovered, Fort Harrell was last seen by the engineers who built the Tamiami Trail in 1917, Beightol said. The three explorers had to fight thick vegetation to get to the site because the highway's construction reduced what was once a robust New River to a meandering creek.

Just the same, Beightol would like to see a trail extended from the Tamiami Trail to the fort site, and a boat ramp on the New River to provide water access.

"My goal is to see it open for recreational usage," he said.

In the meantime, the amateur explorers plan to hunt for other forts. "We just like getting out in the Everglades, going on an adventure, going where people don't normally go," Pernas said. "That's what we do for fun."

kkaye@tribune.com or 561-243-6530.