I believe your Gastler family in Carver County Minnesota may have come from the Nassaband area of Germany (now Poland). This is at 53 degree 57' N., 16 degree 21' East.
My great grandparents in Chaska, August and Emilie (Hasse) Darsow, were from this area in Germany. From LDS microfilm of this area, civil register, I found birth records from parents Wilhelm Janke and Emilie Janke born GASTLER listed. There may have been more listed but copied these because of the Janke name. From the 50 year anniversary book of St John Lutheran Church under "Names of Voting Members who have Signed Our Constitution" I found the following Gastler names: Ludwig, Heinrich, Carl, Frank, Paul C and Otto.
Hope this is some help to you.