NEW YORK, NY.- In 1921, a sergeant walked into a small, dark chapel in Châlons-sur-Marne in eastern France, not far from where French and English troops had pushed back against advancing Germans a few years before.

Clutching a bouquet of red and white roses, the sergeant, Edward F. Younger of Chicago, 23, circled four caskets that held the remains of U.S. soldiers who died during World War I.

A colonel had ordered him to choose one coffin, which would be placed inside a marble tomb at Arlington National Cemetery and represent all the U.S. soldiers killed during the war.

“I couldn’t bring myself to make a hasty choice,” he told The Decatur Daily in Alabama in 1935. Younger stopped at the coffin third from his right, placed the bouquet on it, saluted and left the room.

“Something seemed to stop me each time I passed that third one’s coffin,” he said, describing the selection he made on Oct. 24, 1921. “Something seemed to say, ‘Pick this one.’”

A few weeks later, the remains were entombed overlooking Arlington National Cemetery in Virginia, where today 4,723 unknown soldiers who died in battles dating to the Civil War are buried, along with more than 400,000 other war veterans.

Since 1948, a 24-hour military guard has kept the public from getting near the white marble sarcophagus. But on Tuesday and Wednesday, people will be allowed to walk close to the tomb again and place flowers to commemorate 100 years since its dedication.

Many are expected to visit the monument, which has become a sacred site for veterans as well as visitors who watch the changing of the guard.

The tomb, however, was not always treated with such reverence.

From Hallowed Ground to Picnic Spot

On Nov. 11, 1921, thousands of people marched to Arlington National Cemetery to watch as the coffin Younger had picked was lowered into a marble tomb. In a speech, President Warren G. Harding described how the soldier “might have come from any one of millions of American homes.”

“Hundreds of mothers are wondering today, finding a touch of solace in the possibility that the nation bows in grief over the body of one she bore to live and die, if need be, for the Republic,” he said.

Chief Plenty Coups, the leader of Crow Nation who was invited to attend the ceremony, laid a war bonnet and a rod known as a coup stick across the coffin.

At first, there were no restrictions on the public’s access to the tomb, which visitors could touch and kneel at, said Allison Finkelstein, senior historian at Arlington National Cemetery.

But as the years passed, the hallowed place became more of a public park.

People picnicked around the tomb and even used it as a table for their food. Photographers would linger, offering to shoot photos of visitors, who would sit on it and pose.

At night, couples were discovered “getting excessively romantic on top of the tomb,” said Beth Bailey, a professor of history at the University of Kansas.

Such behavior was not unusual at the time, she said.

“Remember that, during the Civil War, people went out on picnics to watch battles,” Bailey said.

Guarding of the Tomb as a Sacred Ritual

The decision to make one unknown soldier a symbol for those killed and lost in World War I was born in part out of a deep concern that U.S. service members were being left in cemeteries overseas, said Micki McElya, a professor of history at the University of Connecticut and the author of “The Politics of Mourning: Death and Honor in Arlington National Cemetery.”

In 1918, Newton Baker, the secretary of war, promised that the dead would be returned home, but the logistics of bringing back thousands of bodies from Europe were overwhelming and threatened to disrupt relations with England and France, whose leaders did not want to shoulder the responsibility of transporting dead U.S. soldiers, she said.

Some military leaders in the United States also felt that “soldiers should rest where they fell,” McElya said.

Honoring one unknown soldier helped answer the question of what to do about the lost dead.

But as the tomb became more of a tourist destination and visitors grew unruly, veterans became incensed and demanded protections around it, McElya said.

Initially, a picket fence was placed. Then, a chain-link fence.

It was not until 1948 that the 3rd U.S. Infantry Regiment, the Army’s oldest active-duty infantry unit, was assigned to guard the tomb at all hours and keep visitors away, except for official ceremonies.

The whole site around the tomb came to be “understood as a sacred place deserving of reverential treatment, not meant to be trod on by visitors,” Finkelstein said.

This became especially important in 1958, when crypts holding the remains of unknown World War II and Korean War soldiers were placed at the tomb, she said. The tomb also includes an empty crypt that once held the remains of an Air Force pilot who was killed in the Vietnam War but was identified in 1998 through DNA.

In recognition of that, the name Tomb of the Unknowns came into common public usage. But the cemetery still uses the original name, the Tomb of the Unknown Soldier. “The name has not changed,” said Tim Frank, a historian for the cemetery.

A Somber Ceremony Beginning With Crow Prayer

On Tuesday the first people to place flowers at the tomb will be the members of Crow Nation. Their leaders will also recite a prayer that some historical accounts say Chief Plenty Coups gave 100 years ago, according to a spokesperson for Arlington National Cemetery.

When Chief Plenty Coups and other Native Americans were invited to attend the ceremony, it was meant to be an acknowledgment by the federal government of “the significant role of American Indians in the military during World War I and the possibility that the Unknown Soldier could have been an American Indian,” Finkelstein said.

Between 8,000 and 15,000 Native Americans served in the war, she said.

The presence of Chief Plenty Coups was probably the first time that Native Americans were on a national political stage and broadcast to white Americans other than in Wild West shows, said Aaron Brien, the tribal historic preservation officer for the Crow Tribe.

His presence also represented “this weird duality that we’re not being treated fairly at all at the time,” Brien said. “He’s showing the generosity and kindness of Native people, Native people who weren’t even citizens of the country and were living in a time of abject poverty.”

McElya said many Americans assumed the unknown soldier was a white, heterosexual male. But the mystery of his identity has turned the soldier into a potent political symbol. In 1980, for example, gay and lesbian veterans began laying a wreath at the tomb in a ceremony to honor service members who died in battle.

The tomb helped “Arlington become a site that every single American can claim a relationship to,” McElya said. “The unknown is theirs.”

This article originally appeared in The New York Times.