My grandparents were Gassners.they lived in East-Prussia,a part of Germany which is now Russia since 1945.Their ancestors had settled in these parts sometime in the late 1700's.They all came from parts of Austria or Germany which are now annexed by Italy.They had adopted the Lutheran faith and left to avoid religious persecution.
Only lately is the Gassner name spelled with double-s,originally it was spelled with a german sz,like in Gaßner.
Quite a few Eastprussians emigrated in the 1800's to America
due to economic reasons.If you are Lutheran,you more than likely are one of them.