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:
<ul><li><a href="https://en.wikipedia.org/wiki/de:Alemannische_Dialekte" class="extiw" title="w:de:Alemannische Dialekte">Alemannische Dialekte</a></li>
<li><a href="https://en.wikipedia.org/wiki/de:Grenzorte_des_alemannischen_Dialektraums" class="extiw" title="w:de:Grenzorte des alemannischen Dialektraums">Grenzorte des alemannischen Dialektraums</a></li>
<li><a href="https://en.wikipedia.org/wiki/de:Traditionell_r%C3%A4toromanischsprachiges_Gebiet_Graub%C3%BCndens" class="extiw" title="w:de:Traditionell rätoromanischsprachiges Gebiet Graubündens">Traditionell rätoromanischsprachiges Gebiet Graubündens</a> and</li>
<li><a href="https://en.wikipedia.org/wiki/de:Sprachen_und_Dialekte_in_der_Region_Elsass" class="extiw" title="w:de:Sprachen und Dialekte in der Region Elsass">Sprachen und Dialekte in der Region Elsass</a>,</li></ul>
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.
<ul><li><a href="//commons.wikimedia.org/wiki/File:Alemannic-Dialects-Map-German.svg" title="File:Alemannic-Dialects-Map-German.svg">Alemannic-Dialects-Map-German.svg</a>:</li>
<li><a href="//commons.wikimedia.org/wiki/File:Alemannic_language_location_map_in_1950-de.svg" title="File:Alemannic language location map in 1950-de.svg">Alemannic_language_location_map_in_1950-de.svg</a>: derivative work: <a href="//commons.wikimedia.org/w/index.php?title=User:Pyrokrat&amp;action=edit&amp;redlink=1" class="new" title="User:Pyrokrat (page does not exist)">Pyrokrat</a> (<a href="//commons.wikimedia.org/wiki/User_talk:Pyrokrat" title="User talk:Pyrokrat"><span class="signature-talk">talk</span></a>)</li>
<li><a href="//commons.wikimedia.org/wiki/File:Alemannic_language_location_map_in_1950-fr.svg" title="File:Alemannic language location map in 1950-fr.svg">Alemannic_language_location_map_in_1950-fr.svg</a>: <a href="//commons.wikimedia.org/wiki/User:S%C3%A9mhur" title="User:Sémhur">Sémhur</a></li>
<li>derivative work: <a href="//commons.wikimedia.org/w/index.php?title=User:Testtube&amp;action=edit&amp;redlink=1" class="new" title="User:Testtube (page does not exist)">Testtube</a> (<a href="//commons.wikimedia.org/wiki/User_talk:Testtube" title="User talk:Testtube"><span class="signature-talk">talk</span></a>)</li></ul>
CC BY-SA 3.0
<ul><li><a href="//commons.wikimedia.org/wiki/File:Alemannic-Dialects-Map-German.svg" title="File:Alemannic-Dialects-Map-German.svg">Alemannic-Dialects-Map-German.svg</a></li></ul>