In the 1890s, Antietam became one of the first five Civil War battlefields — along with Gettysburg, Vicksburg, Shiloh and Chattanooga — to be put under the administration of the War Department as a park. At the time, said Baracz, one of the chief reasons given was to set aside these places as outdoor classrooms for students of military science.

The tower that now stands near the middle of the battlefield above Bloody Lane was built so soldiers in training — not tourists — could study the terrain, he said. Cadets from West Point and Mids from Annapolis still come to learn from the fight.

At the time of the park's creation, a group of historians and battle veterans drew up a map of about 3,000 acres encompassing the main areas of combat. Within that area, the government was permitted to acquire land for preservation as it came on the market and if funds were available.

For many years, the National Park Service, which took over the park in the 1930s, owned only a fraction of the most sensitive sites. But in the two decades since the National Trust's warning, the pace of acquisition picked up as the federal government stepped up funding. Baracz said the park service now owns about 2,100 acres in the core battle area — over half of which was acquired in the past 12 to 15 years.

For visitors to the park, that has meant a much different experience, Baracz said. With more land in public hands, the park has been able to create a 12-mile trail system that allows visitors to trace the course of the battle on foot.

While the park service was increasing its holdings in the core battle area, state officials and private conservation groups were moving aggressively to protect the approaches to Antietam and South Mountain from intrusive development. In the early 1990s, under Gov. William Donald Schaefer, Maryland became a pioneer in the use of federal transportation dollars and Program Open Space to preserve farmland along the roadways leading to battle sites.

Today the battlefield is not only a place of remembrance, but an economic engine for Western Maryland. According to Headwaters Economics, a nonpartisan research firm, attendance grew from about 280,000 in 2005 to more than 390,000 in 2010 with an economic impact that year of almost $20 million.

Tom Clemens, president of the Save Historic Antietam Foundation, said there are still important properties on and around the battlefield he'd like to see conserved – either by acquisition or easements. But he said there is still some local opposition from property rights advocates.

"When you try to save anything, they argue that you're trying to save everything," he said.

Lighthizer said he'd like to see some of the 1950s-era ranch homes that line Route 65 overlooking the battlefield acquired and torn down. Eventually, he'd like to see the visitor center built at the heart of the battlefield in 1961 moved to a less central location. But he sees no imminent threat of a subdivision or strip mall popping up where armies once clashed.

"Antietam is 95 percent of the way there," he said.

michael.dresser@baltsun.com

Anniversary events

A full programs of lectures, tours, commemorations and other events will be held Saturday through Monday at the Antietam battlefield. Highlights include:

Saturday

Hikes designed to offer an overview of significant battlefield areas. Each is about one mile and will last approximately about 90 minutes.

•10:00 a.m. Cornfield and West Woods, start at the visitor center

•12:30 p.m. Bloody Lane, start at the visitor center

•2:00 p.m. Burnside Bridge, start at Tour Stop 9

Sunday

Longer hikes. Each is about 2.5 miles and 3 hours.

•9:00 a.m. Burnside Bridge and the Final Attack, start at Tour Stop 9.

•2:00 p.m. Prelude to Battle, start at the visitor center

Monday

•3 p.m. Remembrance ceremony at Antietam National Cemetery.

More information at baltimoresun.com