An update - today I located the immigration record for John Corkill and family. John's age at the time of immigration was given as 48 in April 1866. The ages of all others in the group were spot on to their birth year.
Given this, I am going to assume that John Corkill was born 1817-1819. I am going to assume that his father's name was Robert as given on the marriage license. Robert Corkill and Elinor Christian gave birth to a John. The year of John's birth was 1817.
John had a daughter named Elinor.
Is anyone familiar with the Robert Corkill/Elinor Christian family? The place is German.