How are Dutch and German connected through a dialect continuum?

Dutch and German are connected through a dialect continuum that spans the entire territory from the English Channel to the Alps. Within this region, there is no structurally significant linguistic boundary that aligns with the national borders between the Netherlands, Belgium, and Germany. Instead, the transition between local dialects is gradual, moving from one village to the next.1

This continuum is characterized by various isoglosses, such as the Benrath line, which marks the division between High German dialects to the south and the Low German and Dutch dialects to the north and northwest. While standard Dutch and standard German are distinct, their underlying local dialects share historical roots, including Frankish influences. Eastern Dutch dialects, in particular, often exhibit linguistic features, such as specific umlaut patterns, that are more similar to neighboring German dialects than to the coastal Dutch varieties.2134