The traditional distribution area of the western upper german (=alemannic) dialects in the 19th and 20th century. Source: Mainly these articles in the german wikipedia: 
Alemannische Dialekte
Grenzorte des alemannischen Dialektraums
Traditionell rätoromanischsprachiges Gebiet Graubündens and
Sprachen und Dialekte in der Region Elsass,
plus the (younger) literature, which is mentioned there. This area, having been quite stable for at least some 300 years up to the 19th century, saw consecutively more or less strong changes by industrialisation, population growth, migrations and political developments.
Alemannic_language_location_map_in_1950-de.svg
Alemannic_language_location_map_in_1950-de.svg: derivative work: Pyrokrat (talk)
Alemannic_language_location_map_in_1950-fr.svg: Sémhur
Hungraian labels / Magyar feliratok: BáthoryPéter (talk)