The men's howls of pain were lost in the thunder of the cannon fire on the rolling farmland of what is now Antietam National Battlefield, fields made red by the blood of the dead and the dying.

Today, each of the 23,110 casualties from the 11-hour clash Sept. 17, 1862, was remembered with a lighted candle, set out with military precision across the hundreds of acres of the battle's site. For the 11th year, the land still used to grow corn and soybeans became a cemetery for one night, a place for thousands to visit and contemplate the huge number of soldiers who had been killed, wounded or counted as missing in action.

The 1,200 volunteers who began putting short, thick candles in brown paper bags filled with sand at 9 a.m. had them all in place by noon. They returned to light them about 2:30 p.m., and by dusk, the rolling land was dotted with flickering lights that seemed to reach to the horizon.

"It's like a fine-tuned watch," said memorial illumination creator Georgene Charles. "Everyone knows their responsibilities. We have many meetings with the volunteers in advance, but we have a 97 percent return rate each year, so most everyone is experienced."

At 6 p.m., the gates on the south side of the battlefield were opened, and the first of about 4,000 cars started the snakelike procession along the six-mile course, moving at about 15 mph.

Vincent Vorndran, 57, a salesman for a printing company from Charlestown, W.Va., has done all the jobs for the last seven years. This afternoon, he roamed the battlefield site, giving out extra candles and directing groups to their specific sites.

"It's a honor to be here, " he said. "It's a chance to remember the soldiers and to show people what happened here, what 23,000 looks like."

Charles, a business owner from nearby Clear Springs, said the illumination grew out of a 1986 event she organized in which 23,110 balloons were released simultaneously by 8,000 schoolchildren across the state to mark the September anniversary of the battle. The event was so successful that when someone suggested marking the occasion with candles, Charles agreed.

However, in September the corn is still tall on the farmed fields of Antietam. National Park Service officials embraced the plan, but candles couldn't be set out among the crops. Finally, they settled on having it the first Saturday of December, when the fields would be cleared and before the Christmas season got into full swing.

Charles said she needs only 400 volunteers to do the work, but so many people want to participate, she has let the number swell. Few seem to have a strong interest in the Civil War, she said, but rather are interested in volunteering for a community event.

The illumination is noncommercial, nonpartisan and nonprofit, Charles said. Although reenactors representing the Union and Confederate sides set up campfires within the battlefield site to create a tableau for the passing motorists, the event favors neither side of the war.

Antietam is a much studied and discussed battle because it was there that the Union armies under Gen. George B. McClellan and the Confederates under Gen. Robert E. Lee met in a massive, terrifying day-long struggle that created more casualties than any other one-day battle in the war.

Lee had brought the war to Maryland on Sept. 4, an invasion of northern territory but had been driven back by McClellan at South Mountain on Sept. 14. Lee was desperate for a decisive victory in Maryland, and he halted his retreat at the edge of the Potomac River and turned to face McClellan again in the fields north of Sharpsburg, about 60 miles northwest of Washington.

McClellan's 85,000 troops outnumbered the Confederates by about 2 to 1.

The two armies clashed in the rows of corn taller than them, took shelter behind rock outcroppings and poured down a thunderous storm of shot, shell and canister on each other. The guttural scream of wounded horses mixed with the curses and prayers of injured soldiers.

Although McClellan would claim a major victory when Lee took his diminished troops back across the Potomac into Virginia, his failure to chase and destroy the Army of Northern Virginia would cost him his job.

Today, the battlefield was quiet except for volunteers talking softly among themselves. Those who had come to place and light the candles seemed respectful of the ground.

Frank D'Aquila, 70, a retired dentist from Falls Church, was back for his fourth illumination.

"This is a very emotional experience for me," he said. "It's the realization that each light represents an individual, a person. I have in mind that where I place a candle, a young man died."

For high school senior Lee Groff, from nearby Fairplay, this year was her 11th illumination.

"I think it's neat," she said. "I like learning stuff. I'll be here every first Saturday in December forever. I freed up that day on my calendar starting 10 years ago."

CAPTION: A Civil War cannon rests in front of a sea of candles that have been lighted at Antietam National Battlefield to commemorate the 23,110 casualties during fighting in 1862.

CAPTION: A woman lights a candle that has been placed in a paper bag of sand in the field at Antietam. The 1,200 volunteers work in precision to create the illumination.