Thank you. I did have a breakthrough yesterday (before your post) and found William's headstone in the Old St. Patrick's Cemetery, Bay City, MI, listed in Block 3 and 4 survey of the cemetery. Dates on his headstone read 1826 - 1875, which makes sense to me since his child, Maggie, was born in 1874, and the 1880 federal census lists William's wife as a widow. I've attached photos to my tree so you can see them there.