COLD SPRING, Pa. - No one's waiting at the Cold Spring Railroad Station just now, and there are no guests at the Cold Spring Hotel. In fact, there hasn't been a train through in more than 100 years. Only the hotel's walls and foundation remain, and the station was leveled 20 years ago by vandals.

This is a real, live ghost town - one of several in Stony Creek Valley, a remarkable 19-mile-long strip of wilderness without a single inhabitant or public road that lies just 90 bird-miles from Philadelphia City Hall and within two hours' drive of half of Pennsylvania's 12 million inhabitants.

It is one of the largest roadless areas remaining in Pennsylvania, the last surviving section of a vast expanse of streams, mountains, valleys, fields, and forests that Moravian missionaries named St. Anthony's Wilderness in the 18th century.

In the 19th century, it was the scene of a brief but frenzied coal and lumbering boom, and its population reached 3,000 spread over five towns. All that remains are the crumbled walls and foundations of ghost towns with romantic names like Cold Spring, Rausch Gap, Rattling Run, and Gold Mine.

To some, Stony Creek Valley is an arboreal respite whose waters exceed high-quality standards, a hiker's crossroads separating Dauphin County's developed southern part - including Harrisburg - and the rural northern section, and crossing east into Lebanon County. The valley includes the Appalachian Trail and the Horseshoe Trail, and a powerhouse of nature that embraces 1,500 species of plants and animals in just 35 square miles. But to others, it is vacant land, tempting and ripe for development.

Today the sun and shadows are playing tag across boulder-strewn hills, lichened rocks, and vast fields of ferns. Photosynthesis is on the march. The mulching forest floor smells vaguely of rot. Then human footsteps send a herd of deer crashing through the woods.

Politically, Larry Herr and Gene Stilp are oceans apart. Herr, a retired refrigeration mechanic, is a hunter, a trapper, and a top-tier member of the National Rifle Association.

As much as Herr loves the Second Amendment, Stilp loves the First. He is a voluble gadfly, an antinuke Naderite, a constant thorn in the sides of state and local politicians and, above all else, an environmental activist. Yet Republican Herr and Democrat Stilp are in lockstep on one issue - don't mess with Stony Creek Valley.

Just now they are walking beneath the overhanging superstructure of the forest along an abandoned railroad bed, which forms the spine of the valley, paralleling Stony Creek as it meanders between two steep mountains.

The Pennsylvania Game Commission took over the land in 1947 and turned the railroad into Pennsylvania's first rail trail. There are only three access points, and only hunters, walkers, cyclists, and equestrians are allowed in.

"I have old photos that show that this area has not changed substantially in 40 years, except the trees are a little bigger," says Herr, who carries a walking stick and wears a T-shirt that reads, "Not One Foot. Save Stony Creek Valley."

They continue down the rail trail, their boots crunching the gravel underfoot. They are members of the Stony Creek Valley Coalition, a group of no more than 50 people that meets once a month in a room at a pizzeria not far from the valley.

"We do what we can to keep Stony and our cause in the public eye," says Herr, knuckling his spectacles up his nose. "We have an old educational bus that we put into parades. We run a booth at the state Farm Show, and especially try to work with kids so the next generation will love it here as much as we do."

The coalition was formed in 1974 and disbanded in 1983 after Stony Creek became the first area to be protected under Pennsylvania's Scenic Rivers Program. "We thought we were safe," says Stilp. "But we were wrong." The coalition was reconstituted in 2007 when the neighboring Fort Indiantown Gap military base sought the use of about 900 acres of the valley as a buffer for a new target range for tanks and other armored vehicles.

The plan was dropped last year in the face of determined opposition from the coalition. But this summer, the base aroused new suspicions among the coalition members with a proposal to study the problem of errant ammunition that may lie inside the valley.

"Problem?" asks Herr skeptically. "I've been coming in here nearly every day for 30 years and I've never seen a single piece of ordnance."

Indians lived here more than 7,000 years ago, and it was to convert them that the Moravian missionaries came in 1742.

It remained a wilderness until 1824, when coal was discovered. Investors in Philadelphia and New York City formed the Dauphin & Susquehanna Coal Co. and began digging exploratory shafts. Coal was stockpiled until about 1850, when a rail line was completed.

About the same time, a stagecoach road opened between Dauphin, on the Susquehanna River, and Pottsville. The railroad and coal company imported laborers, most of them English and Welsh immigrants who came directly off boats in Philadelphia, and the population of the valley grew to at least 3,000.

After a one-hour steep uphill climb, Herr and Stilp come to a clearing where a huge uprooted tree, separated from its 200-year grip on the soil, lies like a giant shaggy corpse. Just to the right is a hole, 30 feet in diameter and 50 feet deep. "This was the deepest mine shaft in the valley. It went down about 300 feet," says Herr. Two other mines were operating here by 1840.

Herr leads the way onto a walled path. "This was the way to Yellow Spring Village. The miners used to walk here from their homes every day, spend 12 hours in the mines, and then walk back home. The company owned them. It was not an easy life."

Coal quickly became unprofitable here, and by the 1870s Yellow Spring and other towns began to vanish. Lumbering took over for a few decades, but it, too, quickly passed. Nature began to reclaim the land.

To the west of Yellow Spring is the most distinctive geological feature in the entire valley - the Devil's Racecourse, a long, narrow (120-by-3,600-foot) boulder field that looms like some inexplicable topographical error. Rattling Run careens noisily beneath the rocks, though you can't see it.

The old stagecoach road through Yellow Spring became part of the famed Maine-to-Georgia Appalachian Trail, and the logs of long-distance hikers repeatedly refer to this section as one of the most isolated and beautiful along the entire 2,175-mile route.

While the human population of Stony Creek Valley is zero, there are large numbers of deer, coyotes, black bears, bobcats, beavers, ruffed grouse, rattlesnakes, wild turkeys, and songbirds.

The Appalachian Trail passes through the abandoned town of Rausch Gap, where many of the coal-mine pits, their slopes covered with trees and grass, are still in plain view. The stone foundations of dozens of cabins, laid out at regular intervals, can still be seen.

The homes were built by the railroad for the workers and were of a standard size - 28 feet by 32 feet. The railroad tore down the buildings and moved them elsewhere in 1883, and Rausch Gap was deserted by 1910.

Rausch Creek races beneath a handsome stone-arch railroad bridge, and along its banks catbrier, rhododendron, hemlock, and oaks lean over to peer at their reflections. A few yards off the Appalachian Trail is the Rausch Gap Cemetery, with four remaining stones - three of which have 1854 dates. The most legible sits atop the final resting place of John Proud, who was born in England and died in 1854 at the age of 52. The inscription reads:

"Affliction sore long time I bore

"All human skill was vain;

"Till God did please to give me cease

"And free me from my pain."

It's about 31/2 miles due east back to the town of Cold Spring, which got its name from a spring whose 48-degree waters attracted visitors as early as 1775.

A resort hotel was built at Cold Spring, where mineral springs thought to have life-enhancing properties flowed. Wealthy ailing Philadelphians would come here to take the waters.

The Jesuits of Philadelphia had a summer retreat at Cold Spring in the 1870s. The foundation and stone steps of the old hotel are in plain view. As Herr and Stilp exit the game lands on a shale-bottomed, rain-gutted road at Cold Spring, three sand-color-camouflage humvees, topped by helmeted soldiers manning machine guns, pass by on a training exercise.

"We're on Fort Indiantown Gap now," says Stilp. "We're very suspicious about their motives in doing the ordnance survey. We think that if they find enough, they'll take over the land by eminent domain in the interest of public safety."

In a telephone interview several days earlier, Lt. Col. Chris Cleaver, the post's public affairs officer, denied such intentions.

"It's unfortunate that the coalition feels that this is one more attempt to gain access to Stony Creek Valley," he said. "We just feel it is incumbent upon us to do this survey. We have found ordnance in there. One was a Sherman tank round that was live."

Herr's reaction begins with a snort. "Based on years of experience, we don't trust the Gap." Stilp lifts his shoulders in a regretful, concurring shrug.