According to the Architect of the Capitol's website, the last person to do so was President Gerald Ford.
The honor is reserved mostly for elected and military officials, but others have included civil rights activist Rosa Parks and unknown soldiers from both World Wars and the Korean War.
Sen. Jay Rockefeller called Buckles "a wonderfully plainspoken man and an icon for the World War I generation" and said he will continue fighting for the memorial Buckles wanted.
"He lived a long and rich life as a true American patriot," said Sen. Joe Manchin, "and I hope that his family's loss is lightened with the knowledge that he was loved and will be missed by so many."
Capito said Buckles "represented the very best of this great country-service, determination and patriotism."
The family asked that donations be made to the National World War One Legacy Project. The project is managed by the nonprofit Survivor Quest and will educate students about Buckles and WWI through a documentary and traveling educational exhibition.
"We have lost a living link to an important era in our nation's history," said Secretary of Veterans Affairs Eric Shinseki. "But we have also lost a man of quiet dignity, who dedicated his final years to ensuring the sacrifices of his fellow 'Doughboys' are appropriately commemorated."
In spring 2007, Buckles told The Associated Press of the trouble he went through to get into the military.
"I went to the state fair up in Wichita, Kansas, and while there, went to the recruiting station for the Marine Corps," he said. "The nice Marine sergeant said I was too young when I gave my age as 18, said I had to be 21."
Buckles returned a week later.
"I went back to the recruiting sergeant, and this time I was 21," he said with a grin. "I passed the inspection ... but he told me I just wasn't heavy enough."
Then he tried the Navy, whose recruiter told Buckles he was flat-footed.
Buckles wouldn't quit. In Oklahoma City, an Army captain demanded a birth certificate.
"I told him birth certificates were not made in Missouri when I was born, that the record was in a family Bible. I said, 'You don't want me to bring the family Bible down, do you?'" Buckles said with a laugh. "He said, 'OK, we'll take you.'"
Buckles served in England and France, working mainly as a driver and a warehouse clerk. An eager student of culture and language, he used his off-duty hours to learn German, visit cathedrals, museums and tombs, and bicycle in the French countryside.
After Armistice Day, Buckles helped return prisoners of war to Germany. He returned to the United States in January 1920.
After the war, he returned to Oklahoma, then moved to Canada, where he worked a series of jobs before heading for New York City. There, he landed jobs in banking and advertising.
But it was the shipping industry that suited him best, and he worked around the world for the White Star Line Steamship Co. and W.R. Grace & Co.
In 1941, while on business in the Philippines, Buckles was captured by the Japanese. He spent more than three years in prison camps.
"I was never actually looking for adventure," he once said. "It just came to me."