Then, from 6 p.m. to midnight Saturday, Dec. 2, and often beyond, cars slowly drive the route, headlights darkened. Many parks set up holiday displays of lights in different colors and shapes to captivate youth. Antietam uses a flickering flame to transfix its visitors.
"It's an amazing sight, to say the least," says park superintendent John Howard. "I've yet to meet anyone who isn't impacted emotionally one way or the other."
Though the illumination is supposed to end at midnight, it's not uncommon for the last vehicle to drive through the display at 2 or 3 a.m. Organizers have never turned a car away, though they do preach patience for those stuck in traffic while waiting to begin the 35-minute tour. Programs are available at the battlefield's entrance off Md. 34.
The weather will likely impact how many cars visit the illumination, but Chief Ranger Ed Wenschhof said that last year more than 2,200 drove through. That translates to between 8,000 and 9,000 people. If it rains, the event will take place Saturday, Dec. 9.
Volunteers are on hand all night to relight any candles that are accidentally snuffed out. Emergency crews are also on hand if a fire breaks out.
Wenschhof said he is impressed by the dedication of volunteers who return each year to prepare luminaires. At Antietam since 1992, he added that the event is an important reminder of what happened in the battle.
"It's just such a beautiful display of the casualties," he said. "For us, it's one of the best ways to interpret the casualties of the battle. It's a way to get a glimpse of the tremendous loss."
Though people today don't often consider numbers to be large until they are in the millions, Howard says the illumination drives home what happened at Antietam, where Union and Confederate troops clashed on Sept. 17, 1862.
"You don't realize how many people, lives, is 23,110 until you get something to judge it from," he says. "It just looks like thousands and thousands of twinkling stars or campfires in the field."
Howard has worked at the battlefield for five years. On average, he drives the illumination route five or six times during each illumination. Still, he says the event continues to resonate with him.
"It never bores you. It steals your thoughts and makes you think of other things. Sometimes unpleasant things, but sometimes wonderful things," Howard says. "The idea of what these candles represent does not change, and it grows more powerful. I'm here to preserve this battlefield and it's a good reminder to me about what my job is all about."