The bloodiest day in U.S. history took place in the Chesapeake Bay watershed, along a Potomac River tributary called Antietam Creek.

The Battle of Antietam left more than 23,000 men dead, wounded or missing on a single day in September 1862. Many fell before noon. They died in farm fields and woodlands, along orchards, dusty roads and fence lines. Days later, most bodies remained untended.

It was a horrific clash on incredibly beautiful land, just beyond Sharpsburg, MD. Today, the National Park Service maintains more than 3,000 preserved acres of the battlefield to honor the sacrifice that occurred there. The nation is marking the 150th anniversary of the Civil War, and historic significance is top priority.

But while hundreds of thousands of people tour Antietam National Battlefield each year to contemplate the events of 1862, a steady stream of visitors comes for another reason - the vistas, woodlands and wildlife.

The landscape that defined the battle has become a treasure in its own right.

Paddlers travel the creek to the site of an epic conflict at Burnside Bridge. Others stroll along tour roads in early morning light and hike through secluded fields and forests. Birders search for species like the Eastern bluebird, blue grosbeak and grasshopper sparrow. Wildflowers abound.

Acting Superintendent Ed Wenschhof said that Antietam, which so far remains free of intense development pressure, is habitat for 33 plant and animal species on Maryland's threatened, rare, and "watch" lists. It also boasts some of the best quality limestone forests in the state.

Other battlefields in the Chesapeake region play similar roles. Created to honor some of the bloodiest battles in North America, they have become havens for wildlife and people alike. Their preserved expanse of land, with a variety of protected habitat features, become increasingly important as residential and commercial development continue to increase.

The Wilderness Battlefield, near Fredericksburg, VA, only recently escaped close quarters with a Wal-Mart supercenter. Public protest erupted over a proposal to build the store on a privately owned portion of the battlefield immediately next to the national park. In January, Wal-Mart dropped its plans as the dispute moved to court.

"Battlefields like Manassas, Monocacy and Gettysburg are really being encroached by urban development," Winschhof said. "They have become refuges for many species and also refuges of green space for recreation."

The Audubon Society designated both Gettysburg National Military Park and Manassas National Battlefield Park as Important Bird Areas, primarily for their outstanding grassland habitat.

Although Manassas is located in a developed area less than 30 miles from Washington, DC, the park hosts more than 150 bird species, 54 of which breed in the park. Fishermen and birders frequent the grounds, and the dramatic presence of Virginia bluebells draws many visitors each spring.

Bryan Gorsira, natural resources manager at Manassas, said that history now shares the spotlight with nature. "The park's primary mission is the Civil War but as time goes by its significance has become more and more its natural resources."

Photographer Don Cooper began capturing images of Antietam wildlife while working for National Geographic in 1974. He has made daily visits in the spring and fall, and still roams the grounds on a weekly basis.

"Antietam is a just a treasure trove of wildlife," he said.

Cooper likes birds, and birds like Antietam. Among those featured in his work are eagles, owls, raptors, orioles, Eastern bluebirds and a range of aquatic species that linger near the creek. He often explores the Snavely Trail, where he has photographed more than 20 species of wildflowers. Another of his favorites is the Dunker Church.

"Behind the church is a wonderful woods, a hot spot for warblers and humming birds," Cooper said.

The 12-acre tract is called the West Woods, and natural resources manager Joe Calzarette knows it well.

In 1862, the West Woods was a parcel of oak and hickory that saw intense fighting and troop movement. Until 15 years ago, though, the West Woods had ceased to exist. The trees had been cleared for farming and it was Calzarette's job to bring them back.

Under his guidance, scouts, school groups and other volunteers began planting 15,000 bare root seedlings. Today, the West Woods is again a part of the landscape - a success for both historic and natural resources.

But supporting both nature and history well is always a challenge. Managing Antietam's natural resources requires balance, strategy and adjustment.

"We have a mandate to restore the landscape to the way it looked in 1862, but we want to use strategies that are as environmentally sound as possible," Calzarette said.

More than 30 acres of woods and 12 acres of orchards have been restored to their historic locations. When saplings at one site failed to survive in poor soil, the management plan shifted to nurture valuable grassland habitat for birds.

Large areas of the battlefield must be retained in open space to preserve the viewshed and the sites of fields and pastures of 1862. This means that trees can't always grow where Calzarette would like to see them.

"What do you do with a stream bank where ideally you'd have a full buffer of trees, but historically the trees weren't there?" Calzarette said.

As a compromise, some buffers have limited width and consist largely of grasses and shrubs. Wherever possible, especially in back areas of the park along Antietam Creek, saplings claim a wide shoreline buffer.

More than 1,200 acres of the battlefield remain in active agriculture through partnerships with local farmers. The field patterns have remained largely the same in the 150 years since the battle, but farm practices have changed greatly.

"We have agriculture overlaying sensitive karst geology, so water quality is one of our highest priorities," Calzarette said. "We use conservation tillage, rotate crops, limit pesticides, use gravity-fed troughs - all the best management practices we know to keep it historically accurate but environmentally safe."

Gettysburg National Military Park deals with similar issues on a larger scale, with nearly 6,000 acres to manage and 2,400 acres in agriculture. Approximately 2,000 acres are grassland habitat, some of which was created recently to reopen historic vistas.

Gettysburg education specialist Barbara Sanders wants to see natural resources programming increasingly integrated with the park's other offerings. She believes that promoting natural and historical resources as a package will encourage field trips during tough economic times.

"With school budgets so tight, the trend has been to cut field trips," Sanders said. "So I've made some efforts to show that a field trip to Gettysburg is not only valid for teaching social studies and citizenship, but for teaching other subjects too. We have to be all of these things, and not just the place where General Lee brought his army."

The Manassas National Battlefield Park has already been a formal part of the environmental education program for sixth graders in Prince William County, Virginia. Funded by the National Oceanic and Atmospheric Administration Chesapeake Bay Watershed Education and Training grant, students investigated the stream system on the battlefield and learned about its connection to the Bay.

Park managers say that tourists pressed for time often limit their stops to the driving tour, so students and other local residents are usually the first to immerse themselves in the natural heritage of these Civil War sites. But as the surrounding landscape grows more crowded, the region's battlefields continue to coax slower visits from people seeking not just a sense of history, but a quiet streamside respite and the glimpse of quail among the grass.