But the most amazing clue was to be found closer to home. In a trunk in my parents’ basement, I discovered the tale of a little Indian boy who escaped the killing fields curled up in an Army camp stove. The end of that story—one of fortitude, family and forgiveness—isn’t yet written even today.

So I was left to sift through old records, photos and the accounts of others who were there with him. My search took me to ancestry websites, the National Archives and museums in Colorado and Oklahoma. I tracked down my long-lost relatives and buttonholed historians of the Old West. I even met a veteran crime-scene investigator who agreed to walk me through the cold case at the massacre site.

When he died in 1925, one of the last of Colorado’s early settlers, an obituary in the Denver Post included these lines: “Perhaps none of the army of pathfinders had a more thrilling story to tell of how a civilization is built on savagery than Allen. But with him a job was done when it was done, and that was the end of it. In him the historian struck a dead lead that he knew, however, was a living vein of uncounted riches.”

In my own small way, I’m asking the same questions. Unlike the major players in the drama, my ancestor left little evidence of his thoughts or actions that day.

Now, as the 150th anniversary approaches, Native Americans are trying to restart the conversation. A commemoration will be held on the steps of the state Capitol in Denver. The United Methodist Church is investigating its culpability in the affair, given that key figures, including the commander, Col. John M. Chivington, were prominent members. Northwestern University and the University of Denver, both founded by territorial Gov. John Evans, have pored through thousands of pages of official records, letters and other documents. They want to reconcile how a man known for his Christian generosity could have been a party to such an atrocity—and whether they should feel any guilt by association.

William M. Allen, who was 27 at the time, had enlisted in the Third Colorado Cavalry Regiment in response to an urgent call by the governor for volunteers to pursue “hostile Indians.” The ill-trained and poorly equipped unit, composed of farmers, miners, shopkeepers and tradesmen, served for just over 100 days, then melted back into civilian life. Allen went on to local prominence, building up substantial landholdings and serving as a county commissioner. A neighborhood and street in the Denver suburb of Arvada took his name. He rarely spoke of Sand Creek.

Over the next nine hours, the troopers slaughtered up to 200 people, at least two-thirds of them noncombatants, then mutilated the dead in unspeakable fashion. The Sand Creek Massacre scandalized a nation still fighting the Civil War and planted seeds of distrust and sorrow among Native Americans that endure to this day.

His commander, a fiery former Methodist preacher, reminded the men of previous Indian attacks against settlers. “Now boys,” he thundered, “I shan’t say who you shall kill, but remember our murdered women and children.”

As dawn broke over the eastern Colorado prairie on Nov. 29, 1864, a hastily assembled regiment of volunteer U.S. cavalrymen approached their target: a peaceful village of Cheyenne and Arapaho wintering on Sand Creek.

Some of my relatives cringed when I first told them of my plans to explore Sand Creek. “This is Allen business,” declared my 86-year-old uncle. “You don’t stick your nose in stuff that’s old history.”

I have to admit I had my own qualms. I quickly learned, for instance, that William Allen brought back an Indian scalp from Sand Creek. My father and my uncle remember, as small boys, seeing it at family dinners, hanging on the wall of their grandparents’ house between the kitchen and the dining room.

Another artifact sat in my dad’s dresser drawer for decades: a tarnished silver amulet in the shape of a bird, with a half crescent dangling precariously from the bottom. A scrawled note signed by one of my great-great-grandfather’s daughters, Laura A. Brown, described it as a “Beaten silver Charm worn to ward off Death. Taken by the late William Allen from the body of an Indian Killed in the battle of Sand Creek.”

One day last year I drove into the hills east of Denver, to the modest ranch-style home of David Halaas, Colorado’s former chief historian. He was sitting in his living room with another eminent Sand Creek expert, Gary Roberts. When I described my mission, both initially tried to reassure me. Many of the soldiers at Sand Creek didn’t take part in war crimes; some merely guarded captured Indian ponies.

Then I pulled the silver charm out of a plastic bag. Dr. Halaas, his eyes welling up, fled the room. When he recovered his composure, he said, “That’s explosive. To the Cheyenne, that’s a sacred object.” He cleared his throat. “It seems pretty clear that your great-great-grandfather was among the worst of the atrocities.”

A silver amulet taken off the body of a dead warrior at Sand Creek by William M. Allen F. Martin Ramin/The Wall Street Journal

Dr. Roberts, a retired history professor with an extravagant beard and a courtly southern drawl, was philosophical. “It’s a very human story,” he said, “and humans sometimes do terrible things.”

The restless son of a New Brunswick sea captain, William Allen came to Colorado in 1859 as part of the Pike’s Peak gold rush. Nearly overnight, the territory’s population swelled by 100,000 people. They quickly transformed a mining camp on the site of a traditional Arapaho camping ground into a boomtown known as Denver. Gold didn’t pan out, so Allen traded a team of oxen for the homestead rights to 160 acres of rich farmland near the foothills of the Rockies.

The stage for the Sand Creek tragedy was set by people far above my ancestor’s pay grade. Gov. Evans, an early ally of President Lincoln, was determined to bring Colorado into statehood, and that meant settling the land with farmers and lacing it with railroads. The Cheyenne and Arapaho—and the treaty granting them vast swaths of eastern Colorado—stood in the way.

At the same time, the top Colorado military official, Col. Chivington, was itching to build on his fame as a Civil War hero at the expense of the increasingly restive Indians. The political future of the “fighting Parson” depended on it.

By the summer of 1864, tensions were on the rise in Denver. In June, Indian raiders attacked a ranch just 30 miles away. They murdered the ranch manager along with his wife and two small daughters. The bodies, scalped and mutilated, were disinterred and paraded through the streets of Denver.

An 1864 poster recruiting volunteers to enlist in a 100-day cavalry regiment formed to fight ‘hostile Indians’ in Colorado territory. MPI/Getty Images

Hysteria periodically swept the town as rumors spread of imminent attacks. Newspapers published accusations of Indian atrocities, warning darkly that there was only one sure way to deal with the menace. “If there is one idea that should become an axiom in American politics,” the Black Hawk Mining Journal wrote in late August 1864, “it is THAT THE RED MAN SHOULD BE DESTROYED. His existence is a curse to himself and to us.”

Col. Chivington himself argued in a public speech that even Indian children should not be spared. His motto was to “kill and scalp all, little and big,” he was quoted as saying, because “nits make lice.”

When the call came from Gov. Evans for volunteers to fight Indians in August 1864, my ancestor quickly signed up—and then waited. For weeks after the Third Cavalry was formed, there seemed to be little sense of urgency. As the U.S. Army bureaucracy slowly assembled horses, uniforms and guns, the volunteers kept themselves entertained in downtown Denver, running up big bar tabs. Soon they were being ridiculed as the “Bloodless Third.”

According to his service record, William Allen was assigned to Company C, otherwise known as “Morgan’s Battery.” Formed under the command of an accountant-turned-artillery-captain named William H. Morgan, the company included two mountain howitzers. Such weapons, which fired explosive cannon balls and rounds akin to giant shotgun shells, had never been used against Indians in Colorado territory before.

Not that most of the men of Company C would have actually touched the howitzers. According to records kept by Jeffrey Campbell, a retired criminal investigator who now works for the National Park Service, there weren’t many professional soldiers in the bunch. Instead, among the roughly 100 recruits, there were 31 farmers, 11 teamsters, seven miners, a handful of herders and laborers and a trumpeter from Germany. It seems likely that the bulk of them were there as muscle, to provide a protective perimeter on the battlefield.

Path to Infamy Volunteer cavalrymen traveled over 200 miles to reach the scene of the attack. Source: Jeff C. Campbell, Ranger/Interpreter, Sand Creek Massacre National Historic Site

As their 100-day enlistment dragged on without action, there seemed to be plenty of free time. One of his buddies inked a tattoo on William Allen’s left forearm, according to pension records on file at the National Archives.

When the orders finally came to move out, a blizzard had roared through. The men rode their first 80 miles of the 240-mile journey braving 2-foot snow drifts. None of the enlisted men had any idea where they were going; they just knew they were miserable. One enlistee from Company C dropped dead on the trail.

On the afternoon of Nov. 28, the men arrived at Fort Lyon, an outpost on the Arkansas River manned by members of the veteran First Regiment. There, Col. Chivington revealed to local officers his plan to attack an encampment of Indians 40 miles away, on a bend in Sand Creek.

He was met with a torrent of protest. The officers at Fort Lyon well knew that the Cheyenne and Arapaho at the encampment were led by prominent “peace chiefs.” Obeying the instructions of Gov. Evans, the chiefs had placed themselves under the protection of the fort.

One man in particular, a captain named Silas S. Soule, emerged as a leader of the resistance, sealing his reputation as one of the story’s few clear heroes. Capt. Soule, an ardent abolitionist and friend of Walt Whitman, told his fellow officers, “Any man who would take part in the murders, knowing the circumstances as we did, was a low lived cowardly son of a bitch.”

The Third, unaware of the controversy, along with elements of the First Regiment, close to 700 men in all, went on the march that night, arriving just before dawn within sight of an unusually large Indian camp, with some 120 lodges. Col. Chivington himself gave the battle charge, eyewitnesses said in various accounts.

When the bullets started flying, the Indians at first assumed it was some sort of mistake. Black Kettle, one of the chiefs, came out of his tent and raised a pole with an American flag that had been presented to him by the commissioner of Indian Affairs—and a white flag, just in case the meaning of the first was unclear. Greeted with a hail of bullets, he retreated.

Another chief, White Antelope, ran toward the commanders, a scout named James Beckwourth later testified, “holding up his hands and saying ‘Stop! Stop!’ He spoke it in as plain English as I can.” As the firing intensified, according to Cheyenne and Arapaho stories, he folded his arms and calmly began to chant his death song: “Nothing lives long, except the Earth and the mountains.” Shot through with bullets, he died in the creek bed.

The reluctant Capt. Soule declined to participate in the attack and maneuvered his men to one side, as the fighting degenerated into a free-for-all. Over nine hours, the killing field comprised as much as 50 square miles. The real carnage was in sand pits in the creek bed, a mile or so upstream from the village. There men, women and children dug trenches and piled driftwood in front of them.

Initially, several cavalrymen were killed as they peered over the bank, cut down by Indians in the pits. That’s when the mountain howitzers of Company C were wheeled into position. From virtually point-blank range, they blasted the sand pits and everyone in them, according to Mr. Campbell and accounts later obtained through federal investigations.

Eyewitnesses documented acts of wanton depravity. “I tell you Ned it was hard to see little children on their knees have their brains beat out by men professing to be civilized,” Capt. Soule wrote to his former commander Edward Wynkoop. “One squaw was wounded and a fellow took a hatchet to finish her, she held her arms up to defend her, and he cut one arm off, and held the other with one hand and dashed the hatchet through her brain…One woman was cut open and a child taken out of her, and scalped.”

In September 1864, several Cheyenne and Arapaho chiefs met with Colorado authorities near Denver to seek peace. Standing from left to right: Unidentified, Dexter Colley, John S. Smith, Heap of Buffalo, Bosse, Sheriff Amos Steck, unidentified soldier. Seated from left to right: White Antelope, Neva, Black Kettle, Bull Bear, Na-ta-Nee (Knock Knee). Kneeling from left to right: Major Edward W. Wynkoop, Captain Silas Soule. Denver Public Library

Maj. Scott J. Anthony, in charge of one Fort Lyon battalion, later testified that soldiers used a toddler for target practice as he straggled behind his fleeing family. “I saw one man get off his horse, at a distance of about seventy-five yards, and draw up his rifle and fire—he missed the child,” said Maj. Anthony. “Another man came up and said, ‘Let me try the son of a bitch; I can hit him.’ He got down off his horse, kneeled down and fired at the little child, but he missed him. A third man came up and made a similar remark, and fired and the little fellow dropped.”

No such accounts made it into the first reports of Sand Creek in Denver newspapers. The men of the Third returned to Denver for a hero’s welcome, parading their souvenirs. “Cheyenne scalps are getting as thick here now as toads in Egypt,” the Rocky Mountain News reported. A Denver-area theater displayed the grisly trophies on stage.

Lt. Col. Leavitt Bowen, the commander of my great-great-grandfather’s battalion, did them all one better. He carried White Antelope’s ears in his pocket and produced them in Denver bars to win free drinks.

As reports filtered to politicians and newspapers back East, the story morphed. The Chicago Tribune called it “an act of hideous cruelty garnished with all the accessories of fraud, lying, treachery, bestiality.” A congressional committee later reported: “It is difficult to believe that beings in the form of men, and disgracing the uniform of the United States soldiers and officers, could commit or countenance such acts of cruelty and barbarity as are detailed in the testimony.”

As time went on, popular culture reduced the Thirdsters to stereotypes. In his 1970 best-seller, “Bury My Heart at Wounded Knee,” Dee Brown wrote that the troopers had spent their night ride to Sand Creek engaged in “heavy drinking of whiskey.” They were lost souls in the film “Little Big Man” and psychopaths in “Soldier Blue.”

In real life, the troopers of the Third left their marks on the West. The regiment’s commander, Col. George Laird Shoup, largely escaped censure and went on to serve as a U.S. senator from Idaho. Capt. David H. Nichols became Colorado’s lieutenant governor and gave his name to a dormitory at the University of Colorado, until students demanded the name be changed to Cheyenne Arapahoe Hall in 1989. Silas Soule, who blew the whistle on Col. Chivington, was gunned down on the streets of Denver in 1865; his murderers were never brought to justice. Nor were any of the perpetrators of Sand Creek.

As for my great-great-grandfather, he went on to build a life in the Denver area, becoming an early investor in an irrigation project that fueled the rise of the Denver suburbs. According to his obituary, he never touched alcohol or tobacco.

He remained a tough man, and quick to anger. On a Sunday evening in the summer of 1884, William Allen visited the farm next door to see why his irrigation ditch had dried up. He discovered that his neighbor, Amos S. Sampson, a former Wild West performer who went by the stage name “Rattlesnake Dick,” was stealing the water for his own crops.

William Allen: A Family Portrait William M. Allen posed in approximately 1905, when he was in his late 60’s, in Arvada, Colo., with his grandson Elbert Allen, grandfather of the author. Allen Family 1 of 3 • • • • • 1 of 3 Show Caption William M. Allen posed in approximately 1905, when he was in his late 60’s, in Arvada, Colo., with his grandson Elbert Allen, grandfather of the author. Allen Family

According to an account in the Denver Republican, Sampson acknowledged he had placed a dam on the ditch and added, “I’ll shoot the first man that tries to take it out.” Allen picked up a shovel and replied: “Then go ahead with your shooting.”

Sampson opened fire with a rifle. He missed. William Allen’s assistant returned fire with a shotgun. He missed. My great-great-grandfather then dropped his shovel and began rapid-fire shooting with a revolver. He didn’t miss. Sampson fell gravely wounded, and the assistant finished him off with his shotgun. I can find no evidence that any charges were filed; the general feeling in the community seems to have been that Rattlesnake Dick got what he deserved.

In his later years, my ancestor delighted in telling tales of the Old West to his grandchildren, and raised the hair on the back of their necks with Indian war whoops. Old age was not kind to him, though, and I couldn’t help but compare his death to White Antelope’s. According to medical records on file with the pension department, he became so deaf that he could barely understand words shouted into his ear. Senile and all but blind, he needed a full-time attendant “to prevent his doing injury to himself and others and to his property.” Late on the night of July 31, 1925, deep into his 88th year, the old pioneer finally breathed his last.

But the story didn’t end with William M. Allen.

In December 1864, the boys of Company C were in a pickle. Fresh from the killing grounds of Sand Creek, they were on their way back to Denver loaded with trophies: scalps, body parts, buffalo skins, headdresses.

Then, they realized they had an unexpected guest. A small Indian boy had somehow escaped the slaughter. He was burrowed in the camp stove. I first heard about this twist when I found a manuscript tucked away in an old chest belonging to my father. There, typed by someone who identified herself as the wife of one of William Allen’s grandsons, were a few tidbits of the stories he told of early pioneer life in Colorado—including this one, the only specific reference to Sand Creek:

“Though the cammand of Colonel Chivington has since become controversial,” the scribe began, then crossed out the adjective and scribbled “debatable” in pencil, “the stories that William Allen told his grandchildren about this period of his life emphasize the personal aspects of the people involved in the struggle. Another of the favorites concerned a small Indian boy who stowed away in the oven of the camp stove. He was not discovered until the company had covered much of the long trek back to Denver. The Indian boy became a favorite of Denverites, as he lived on the streets of Denver and entertained by-passers with Indian tricks in exchange for pennies.”

The clear orders were to take no prisoners. On the way back from Sand Creek, another baby was discovered tucked away in a grain wagon. It was left to die on the cold prairie.

But Company C wasn’t of a mind to follow orders. Was their Christian training kicking in? For some of the men, no doubt. But I believe that others in the unit had darker motives: They saw the potential to make some money. After all, what could make a better trophy than a real, live Indian boy?

The story picks up deep in an unpublished doctoral dissertation completed in 1984 by historian Gary Roberts. The Thirdsters did in fact bring back an Indian boy with them. Lt. Col. Bowen—the man with White Antelope’s ears in his pocket—declared him to be “the only son of Black Kettle, the Head war chief of the Cheyenne nation.” As the troop was disbanding, Bowen authorized a corporal in Company C named Lemuel Graham “to take, keep, and treat this boy the same as he would were he his own child.”

Along with a partner from Company C, a farmer named Jesse Wilson, Graham promptly made him the main attraction in a circus that also included rattlesnakes and a bear. Mr. Graham bestowed upon the boy his new white name: Wilson R. Graham.

But by 1865, the government was parlaying with the Cheyenne and Arapaho, trying to bring an end to the bloodshed. There was a sticking point. The chiefs demanded the return of the little boy.

The commissioner of Indian affairs instructed the then-Colorado governor, Alexander Cummings, to locate him. He reported that he was no longer in the territory. The Army, too, pressed the search, finally picking up his trail in Indiana. By one account, soldiers staged a dramatic backstage rescue of the boy, now about five years old, just as a performance was concluding.

The child returned West to considerable media acclaim. In 1867, he joined the expedition of Gen. Winfield Scott Hancock, who was traveling to the plains to punish hostile Indians. The boy made a favorable impression on a young George Armstrong Custer. “He was dressed comfortably in accordance with civilized custom; and, having been taken from his people at so early an age, was apparently satisfied with the life he led,” Gen. Custer wrote in his book, “My Life on the Plains.”

After it was determined that he wasn’t Cheyenne at all, but Arapaho, he was handed over to a chief of that tribe, Little Raven. He received a new name: Tom White Shirt, and was brought to Oklahoma, where some of the demoralized Indians had been resettled. For a time, he continued to interest the press. Henry M. Stanley, the English journalist who would go on to win world renown for locating Dr. Livingstone in Africa, met up with the child while on a newspaper assignment.

Flourishing Family Over eight generations, the White Shirt clan has expanded to at least 330. 1st

Gen. 2nd 3rd 4th 5th 6th 7th 8th

“This boy is rapidly forgetting the English language,” he wrote. “He is efficient in the use of the bow and arrow, and has acquired prominence among his many playmates on account of his varied accomplishments. His feats of leaping and wrestling command the respect of the Arapaho elders. His knowledge of the English language is a source of constant admiration, and his many-bladed jack-knife is an object of envy to his brother braves.”

Tom White Shirt, in the manner of many child stars, eventually dropped out of sight. He married multiple times. He was given 160 acres to homestead—same as my great-great-grandfather—and lived out his days near Calumet, Okla.

His life was far from easy. He never learned to read or write. The federal government viewed Native Americans as incapable of handling their own affairs. Files in the Oklahoma History Center show that Tom White Shirt had to seek permission to buy clothing or a train ticket. In 1925, he asked a local supervisor if he could withdraw $60 from a bank account held in trust, $25 of it for Christmas and $35 to lend to a man named Peter Hoof. “I do not like this loaning but Pete is such a reasonable and good fellow I will say yes,” the supervisor wrote. Tom White Shirt signed with a thumbprint.

The 1894 Indian census shows Tom White Shirt at 29 years old, living with a wife, White Cow, a 9-year-old son, Falling Off The Horse, and an infant daughter, Georgia. By 1920, the son, renamed Earl White Shirt, had himself married, to a woman named Good Warrior. He had three daughters and two sons. Earl went into show business, joining a famed Oklahoma Wild West show as a trick shooter.

By the time Tom White Shirt died in 1933, around the age of 70, the clan he founded was enthusiastically repopulating the plains. Earl’s five children had nine children, who in turn had 49. I was able to identify 135 people in the sixth generation, and 122 in the seventh.

There are soldiers and social workers in the White Shirt family tree, alcoholism counselors, tribal leaders and a documentary filmmaker. Some live in poverty and some have struck oil. One of Tom’s great-great-grandsons, James Earl Whiteshirt, known to his friends as “Jimmy,” earned a Medal of Valor from the Tulsa police department for risking his own life to save a shooting victim. At 63, he alone has seven children, 20 grandchildren and seven great-grandchildren. By last week, the White Shirt line was up to at least 331.