Hi Susan. Do you have him on any US censuses? That should tell you when he came to the US, and also if he became a US citizen. At some points in history Tonning was in Denmark, and the parish records are at http://www.arkivalieronline.dk/http://www.arkivalieronline.dk/http://www.rootsweb.ancestry.com/~dnkcen/http://www.rootsweb.ancestry.com/~dnkcen/ - is a guide in English to how to use the above site. You want to look for church records in Tønning, which is in Skanderborg amt.