— On this plot of nondescript land tucked away in rural Illinois, Bill Kleiman sees more than just rows of dead cornstalks and black dirt.

He sees a slice of earth slowly transforming back to its roots, a tallgrass prairie haven that bison will soon call home after a nearly 200-year absence. Bison hooves hit the ground here in October, a return that experts say is essential to restoring the prairie in the Prairie State.

And so, on a recent Saturday, Kleiman and a team of volunteers scrambled across the Nachusa Grasslands and tackled various tasks to convert the land and prepare for the bison, a project nearly 30 years in the making.

"We humans are the stewards of the planet," said Kleiman, project director of Nachusa, a preserve that is owned by The Nature Conservancy. "We need to do our job in caring for these landscapes."

At least 30 million bison grazed the North American prairies in the 1500s, allowing plants to grow and attract native animals. But over-hunting killed most of the iconic creatures, crushing the population to less than 1,000 by the 1800s, according to the U.S. Fish and Wildlife Service.

With the help of ranchers and conservationists, bison have made a comeback. A 2007 U.S. Department of Agriculture census shows more than 198,000 bison on private properties across the country, with more than 1,200 in Illinois. An additional 20,000 bison roam public land in the U.S.

The state's prairie acreage has declined, too. Before settlers arrived, more than 19 million acres of prairie covered Illinois. Most of that was destroyed to make way for crops. Today an estimated 2,496 acres of high-quality prairie remnants remain, according to the Illinois Natural History Survey.

Scientists and conservationists agree that grazing, along with fire and a dry climate, help maintain prairie. They point to other preserves across the Midwest with bison that have seen the habitat return.

"That force and the interactions of tallgrass, the plants and animals … that process is what makes a prairie a prairie," said Jeff Walk, director of science for TNC in Illinois, an environmental nonprofit. "It's really time we brought it back."

Ninety miles west of Chicago, staff and volunteers have worked since 1986 to restore Nachusa, a 3,100-acre mosaic of agricultural land and prairie fields.

By taking seeds from the prairie remnants, volunteers have replanted native species like wild petunias, hazelnuts and hawthorn berries. So far about 2,500 acres have been planted to prairie fields. Volunteers have also participated in controlled burns, another key to keeping the prairie alive.

Nachusa's success comes in large part because of its strong base of volunteers, some of whom come from nearby towns and others who travel weekly from the Chicago area. Inspired by the work at the preserve, a few have even bought property nearby.

"We have found the draw to that environment so intense that we wanted to literally every weekend make the journey to be a part of it," said Lisa Lanz, 45, a volunteer from west suburban Indian Head Park who, along with her partner, bought land 3 miles from Nachusa.

"The work they're doing is special," added Jay Stacy, 66, a longtime volunteer who moved from Chicago to nearby Oregon 20 years ago. "They're saying we can reclaim land as best we know how."

Bringing bison back to the prairie had been talked about for decades, but a few years ago, Walk said, The Nature Conservancy produced a study that showed the project was doable.

Since then the organization has raised about half of the $1.2 million needed to build a corral and a 6-foot-high steel-and-wire fence and pay for transportation, among other costs, said Molly Rand, the organization's Illinois director of philanthropy.

Meanwhile, volunteers and staff have visited roundups across the country to see how experts handle the animals.

"We're trying to take the best from each one of those and pick the really good things we really liked and combine them into a system we can use," said volunteer David Crites, 53.

Thirty to 50 bison will arrive this fall at Nachusa in livestock trailers from Wind Cave National Park in South Dakota and other TNC preserves. The conservancy has reintroduced bison to multiple preserves across the country.

The Illinois animals, including some pregnant ones, will roam 1,500 acres year-round, eating grass on that site and drinking from a nearby creek. The staff wants the number of bison to increase, adding that the preserve can hold about 100 animals. Eventually, any excess bison will be sold for meat production to pay for the cost of the project.