It is terrible to hear of the passing of Frank Buckles, but what a life that man lived! It is greatly unfortunate that we are losing these very last human-attachments to that time period and that war - much like what my dad saw in the 40's and 50's, which was then the last Civil War vets passing away.
Thinking about the life that Frank Buckles had, it is even more amazing, for me personally, considering the fact that my great grandpa, who went to France in 1918 as part of the AEF, and my great, great grandpa on the other side of my family, who trained for going to war in 1917/1918, but thankfully never had to, both passed away roughly a half century ago!
Just a little correction on the title of this thread...Frank Buckles was the last, known, U.S. WWI veteran. I know of Claude Choules in Australia, and Florence Green in Britain, both of whom are surviving veterans of WWI - there may be more that I cannot recall at this time.