ANTIETAM BATTLEFIELD, Maryland -- The bloodiest single day in American history did not occur when the Twin Towers fell, or when Pearl Harbor was attacked, or when a deranged but legally armed killer opened fire at a theatre, a temple, a high school or Fort Hood.
It did not happen in Khe Sanh or Inchon or Normandy or Kandahar or the Ardennes Forest, but in a late-summer Civil War travesty in the hills of Maryland that ended in stalemate, left 23,000 men dead or wounded before nightfall and made an indelible mark on Canada.
"Imagine you have joined the Fourth Rhode Island Volunteer Infantry for a bounty of $300," a young expert is saying to a group of camp-followers as we march across the ground where that awful half-day of hell called the Battle of Antietam took place, 150 years ago this weekend. "You are college students who think that a few weeks away from your studies will be good for you."
"A week ago, you were hanging around Hartford, Conn. You have never been in combat before. You just got issued your rifle the night before. Half of your officers have quit in an argument over who will be your commander.
"Now you suddenly find yourself in a place where, every second for 12 full hours, a man gets shot."
The saga continues. You are 5-6 and you are under attack in a cornfield in mid-September, when the stalks are six feet high. You can't see anything but corn, but you can hear the guns and the minié balls shredding human flesh and the screams of the wounded. Now, coming right at you through the cornstalks are troops wearing the same blue uniforms you are wearing.
But they are the enemy, and they are killing your friends.
In front of your advancing line, the Sixteenth Connecticut fires a volley. The rebels shoot back, and as soon as that happens, the Sixteenth Connecticut panics and runs away. The cowards swarm a little stone span, fly across Antietam Creek and plow right through the ranks of the Fourth Rhode Island, just as you are trying to move forward over the same bridge.
Now imagine that one of the Rhode Islanders fighting the Confederates in their pilfered Union uniforms that rainy late-summer day in 1862 is a young émigré from Montreal, a member of a Providence brass band who has joined the Union Army for the money and the thrill and who has been assigned to stretcher duty, only to find himself in the centre of the carnage at Antietam, wounded in the hand, or possibly only on the thumb, though other sources say he got it in the leg.
Discharged a few weeks after the battle, he resumes his musical career, travels back and forth and back and forth from Lower Canada to Massachusetts to Louisiana to South America to Paris to New York. In 1880, commissioned to toss off a patriotic melody for the Société Saint-Jean-Baptiste de la Cité de Québec, he writes the music to go with a French-language poem called O Canada that will not be performed in English for another 20 years.
This is true: Calixa Lavallée, the man who created the melody for what would become -- finally, in 1980, on the song's centennial -- Canada's national anthem, fought for the North in the War Between the States and was wounded at Antietam, on America's bloodiest day. Is this something that everybody knows? (I didn't, before now.)
"Why did so many Québécois come down to New England and join the Union Army?" I ask our tour guide, Robert Grandchamp, a 26-year-old amateur historian of the Rhode Island regiments whose own father's father left Quebec in 1906.
We have paused beside the same cornfield where Lavallée and the college boys of the Fourth were slaughtered so Mr. Grandchamp and some other folks may recite the names of the dead.
"A lot of them joined up in Vermont because the state offered an additional bounty of seven dollars a month," he says. "The money was so enticing that not only did Québécois cross the border to enlist, so did a lot of British soldiers who were stationed in Canada. But Lavallée had probably been in Rhode Island since the 1850s."
Robert Grandchamp has driven down from Vermont, where he works for the Department of Homeland Security, to lead today's walking tour. Accompanying him on the long drive are his mother and her mother.
"This has been lifelong," Mom tells me. "When all the other kids wanted to go to Disney World, he wanted to go to battlefields. If a blade of grass had a monument on it, he wanted to be there."
"He's always in a cemetery," Grandma says. "He ordered so many tombstones for the forgotten soldiers that he calls 'his veterans,' that my front yard looked like a graveyard."
Through such passions are great events preserved beyond the memories of those who lived them.
"After Antietam," Robert Grandchamp says, "the Fourth Rhode Island is encamped down near Harper's Ferry. They are so dejected after what happened in the cornfield that, in at least half a dozen instances that I know of, families in Quebec mailed boxes of civilian clothes to soldiers who simply put them on, walked out of camp, made their way to Washington and took a train to Montreal or Quebec City.
"Desertion did not carry the stigma than that it does now. It strengthened the army to have foreigners leave. The army would have been glad to get rid of them."
Allen Abel is a Brooklyn-born Canadian journalist based in Washington, D.C.