Peggy, I can offer you a possibility as to the ancestors of your William H. Burbridge who "just seems to have dropped out of the sky."A Roland Burbridge, b 10 April 1819, who married Emeline Hoag in 1847, had, according to his obituary (provided to me by Randy May), six children, the list of whomin the obituary was headed by Wm. H.The obit goes on to say that Wm. died in 1896.Roland farmed near Greeley, IA starting in 1866.
From the dates in the foregoing it appears that this could be your William.If you feel this is your man I can provide info on two preceding generations of this Burbridge line.