For centuries, Russian Old Colony Mennonites have been associated with a triglossic separation of language use into the realms of Sunday life, daily life, and community-external life. The languages involved in this situation varied depending on the location of the settlements. A new development is underway in migrant communities in Kansas, in which triglossia can no longer be maintained as the result of changes in the social dynamics of the region (such as school and church organization). This paper presents data from a Mennonite community of Plautdietsch-English speakers in southwestern Kansas who formerly lived in Mexico, and which is now undergoing a shift from being affiliated with traditional Mennonite churches to churches defined by Anabaptist Evangelicalism. This religious shift is reflected in a linguistic shift, shown by language use and attitudes described by 35 speakers in oral history interviews. The results are embedded in principles of Fishman's (2006) sociology of religion and language and support Salmons' (2005) model of verticalization, i.e., the shift from local to regional/national structures is related to language shift. Crucially, this change happened within one generation of migrant speakers due to the fundamental differences in societal organization from their previous lives.