By the early mid-20th century, social, political and economic factors such as urbanization and severe persecution during World War I, contributed to a general shift from German to English[citation needed].

The Wisconsin city of Freistadt, for example, was founded by 300 German Lutherans from Pomerania, who were escaping Prussian religious reform and persecution.

[9]: 348  Both their faith and maintenance of their East Pomeranian dialect were important to the Freistadters: although the city was founded in 1839, there were still East Pomeranian speakers in Freistadt well into the end of the 20th century[citation needed].These German speakers were from many different regions and states, such as Mecklenburg-Schwerin, Pomerania, Posen, Rhineland, Westphalia, Switzerland,[10] Bavaria, Luxembourg, Baden, Saxony, Hesse, Württemberg, and Austria.

[2]: 42  Schools fully switched to English by the early 20th century, which partially contributed to the gradual decline of German heritage speakers[citation needed].

Previously, researchers have looked at heritage languages to study incomplete acquisition or L1 attrition (Polinsky, 1995; Sorace 2004; Montreal 2008)[citation needed], yet speakers of Wisconsin German do not fit into either of those categories.

[1]: 2  This means that their German, including grammatical features such as dative, would have already been acquired,[1][12] if it existed in the speakers' heritage language.

[1] However, in Wisconsin German, while heritage speakers appear to no longer show use of the dative case, they have developed new morphosyntactic features.