I have been stuck on this person so long that I welcome any clues!

I am searching for my earliest known Pelkey ancestor, John Pelkey (born between 1824 and 1830, died in 1880). Records conflict, but I believe he was born in Vermont or Canada, possibly Maine. Most records say Vermont. He married Elizabeth Athey and was in Washington County, Pennsylvania by 1860. He served in the Civil War in the 18th PA Cavalry.

I am stuck finding his parents and more evidence of his birth. Any help or suggestions are welcome.