Conversation so far:
when did the last american revolutionary war veteran die
John Gray, one of the candidates for last surviving U.S. veteran of the American Revolutionary War, died on March 29, 1868.
Where was the last surviving U.S. veteran John Gray from
Known as the last surviving Ohio veteran of the American Revolution, John Gray was born at Mount Vernon, the home of George Washington.
At what age did the the last surviving U.S. veteran John Gray enlist
John Gray enlisted at age sixteen and was present at the Battle of Yorktown.
Where did the last surviving U.S. veteran John Gray go after the war
After the war, John Gray moved to what would become the state of Ohio.

Question: How old was the veteran when he died
Self-contained rewrite: How old was the last surviving U.S. veteran John Gray when he died