My father was born in 1928 and remembers when Civil War veterans were still alive. I'm sure that it is not unrealistic to think that some of those may have been alive at the same time as the last of the Revolutionary War veterans. My point being that we are not that far removed from that era if you consider that you could converse with my father today about the fact that he may have been able to talk to people that remembered the last of the Revolutionary War vets.
