Do you mean by this that Hoch-Deutsch was spoken in the northern parts and Nieder-Deutsch in the south of Germany?

No, I meant that Low German was spoken in the flat lowlands in the North (Hamburg, Schleswig-Holstein and Mecklenburg-Vorpommern) and High German in the mountainous areas (Central and Southern Germany). Technically, there are some German dialects called Central German (or Mitteldeutsch) in a sort of buffer between Niederdetusch and Hochdeutsch. Kölsch and Bönnsch are Central German (Franconian) dialects, spoken in Cologne and Bonn respectively. They share some characteristics with Dutch and Low German: e.g., Kölsch hä ~ High German er 'he', Appel ~ Apfel 'apple', et ~ es 'it', wat ~ was 'what', etc.

Ceci n'est pas un seing.