Buckles, who also survived being a civilian POW in the Philippines in World War II, died of natural causes Sunday at his home in Charles Town, biographer and family spokesman David DeJonge said. He was 110.
Buckles would have want people to remember him as "the last torchbearer" for World War I, DeJonge said Monday.
Buckles had been advocating for a national memorial honoring veterans of the Great War in the nation's capital and asked about its progress weekly, sometimes daily.
Fight To Remember WWI Veterans Buckles Honored in 2008
"He was sad it's not completed," DeJonge said. "It's a simple straightforward thing to do, to honor Americans."
When asked in February 2008 how it felt to be the last of his kind, he said simply, "I realized that somebody had to be, and it was me." And he told The Associated Press he would have done it all over again, "without a doubt."