While wandering through the woods and prairies of the Pilot Knob area in Mendota Heights last week, Gail Lewellan overheard a fellow hiker and college student telling his friends about its historical significance.

"It was so heartening for me," said Lewellan, co-chair of the Pilot Knob Preservation Association.

Lewellan and many others have fought for recognition of Pilot Knob as an important cultural and historic site for nearly 15 years. This spring, it achieved a milestone — it was named to the National Register of Historic Places, an honor that advocates and American Indians hope will garner it additional protection from development.

"This designation opens the door to a new level of public awareness," Lewellan said.

The 112-acre site is composed of public and private land, including about 35 acres owned by Mendota Heights, a cemetery and several homes.

Dozens of townhouses were nearly built there in 2002. The outcry from Indians, environmentalists and historians halted the development and led to the formation of the nonprofit Pilot Knob Preservation Association, and efforts to protect the area gained steam, Lewellan said.

Pilot Knob is noteworthy in the story of Minnesota's statehood and environmentally significant because it overlooks the confluence of the Minnesota and Mississippi rivers. Known as Oheyawahi in Dakota, which means "a sacred place much visited," it is a burial ground and cultural site for American Indians.

"It's significant in the Dakota experience," said Iyekiyapiwin Darlene St. Clair, a professor of American Indian studies at St. Cloud State University and member of the Lower Sioux Indian Community. "For me, as a contemporary Dakota person, this is a place that I continue to go and visit."

Early European explorers' letters referenced the dramatic view from Pilot Knob, which once included a distinctive knob formation atop its hill. The knob had been used as a landmark to guide steamboats down the river until it was removed in 1925 by the owners of a nearby cemetery. Illinois Sen. Stephen Douglas suggested it be Minnesota's territorial capitol in 1848 and later the Treaty of 1851 was signed there, ceding 25 million acres to the U.S.

During the winter of 1862-63, a internment camp for the Dakota was located across the river at Fort Snelling. Many died, and some were buried on Pilot Knob.

"I'm really delighted that it's listed," said David Mather, the National Register archaeologist for the Minnesota Historical Society. "That's a nice step forward."

It's relatively rare for a site, rather than a building or structure, to be included on the registry. Dakota County has only one other such site, Mather said.

The site's journey to the National Register has been complicated. In 2003, the state review board approved its eligibility for the list, but because its private owners at the time objected, the effort stalled, Mather said.

Mendota Heights already owned about 9 acres on the site and acquired 25 more between 2006 and 2008 using grants and funds from the state, city, county, organizations and individuals.

Efforts to restore the city's parcel to its pre-European settler state — prairie with stands of bur oak trees — began a decade ago, said Wiley Buck, program manager for Great River Greening, a nonprofit that does ecological restoration work.

"It was a pretty disturbed site," Buck said. "It's been quite a transformation to take it from that to a functioning ecosystem."

Today, sheep and goats graze the land, chomping on buckthorn and nonnative grasses. A trail system with interpretive signs welcomes visitors and shares information.

Lewellan said she wants the listing to add to people's awareness of Pilot Knob, especially its American Indian significance. The city could still build on the part of its parcel that is zoned industrial, but Lewellan said she hopes the designation will stave off development.

"They've preserved history," Lewellan said. "They've chosen to do the just and right thing."