Trust me, this had never happened before, and I'm still awestruck by that response!One dear soul even went so far as to send copies of census images from 1880 through 1930, so you can imagine the wealth of information I now have.
I haven't come across anyone by the name of Harkness in my line, but thanks to a link included in another post about the deDuysters, I think I may now have at least a partial (and somewhat humorous) answer to why they ended up in Burford, Brant, Ontario, Canada for a time:
"In his "History of Duchess County"...Smith states that Gideon Osterhout and Derick [deDuyster] Dutcher bet their farms upon the result of the war of the Revolution. Dutcher lost and gave up his farm."
The deDuysters, (unlike those who arrived later only to have their last names changed for them as they passed through Ellis Island,) had lived in NY since the 1600's and kept the original spelling of their last name.So, the thing I can't figure out is why all of Direck deDuyster's children ended up using Dutcher?
Also, like your Harkness family, sometime before March of 1874the Dutchers had returned to the U.S. and were living Minnesota.