I too am trodding down the Elderkin path. I think John Plinn Elderkin of Wood Ohio is the father of my great grandmother, Mary Elderkin Baird. A Mary Elderkin was the first wife of David R. Baird of St. Clair County, Michigan. There are no 1850 census records for any Elderkins in St. Clair County so I'm assuming she some how made her way from Ohio to Michigan.
Do you have any information on the Ohio Elderkins.