Northern Germany generally refers to the Sprachraum area north of the Uerdingen and Benrath line isoglosses, where Low German dialects are spoken. These comprise the Low Saxon dialects in the west (including the Westphalian language area up to the Rhineland), the East Low German region along the Baltic coast with Western Pomerania, the Altmark and northern Brandenburg, as well as the North Low German dialects.
Although from the 19th century onwards the use of Standard German was strongly promoted especially by the Prussian administration, Low German dialects are still present in rural areas, with an estimated number of five to eight million active speakers. However, since World War II and the immigration of expellees from the former eastern territories of Germany, its prevalence has steadily reduced. Besides which, Frisian is spoken in East and North Frisia, as well as Danish (Standard and South Jutlandic) in parts of Schleswig. From a linguistic and cultural perspective, Northern Germany is linked to the Netherlands, Scandinavia and England. For example, the German word for butcher is Fleischer or Metzger in the middle, east or south of Germany but is called a Schlachter in Northern Germany, resembling the Scandinavian terms for butcher, slagter/slakter. Other examples are the word for potato, which is Erdapfel in much of Southern Germany, Austria and Switzerland, but Kartoffel in Northern Germany and in Danish; the North German verb kieken (meaning to look), resembling the Danish kikke/kigge, or Norwegian kikke (to look); or the word for the fruit orange, which is Orange in standard Germand, but Apfelsine in Northern Germany, similarly to the Dutch (appelsien/Sinaasappel), Frisian (aapelsiin) and Scandinavian languages (appelsin/apelsin). Additionally, Jansen/Janssen, Hansen, and Petersen are the most common surnames in the far north of Germany (Lower Saxony and Schleswig-Holstein), which are also some of the most common surnames in Denmark (albeit with Jensen for Jansen). Hansen is the single most common surname in Norway, the third most common surname in Denmark, and the third and fifth most common surname in the North German federal states of Schleswig-Holstein and Hamburg, respectively.
The key terrain feature of Northern Germany is the North German Plain including the marshes along the coastline of the North and Baltic Seas, as well as the geest and heaths inland. Also prominent are the low hills of the Baltic Uplands, the ground moraines, end moraines, sandur, glacial valleys, bogs and Luch.
These features were formed during the Weichselian glaciation and contrast topographically with the adjacent Central Uplands of Germany to the south, such as the Harz and Teutoburg Forest, which are occasionally counted as part of Northern Germany. Likewise the Altmark in Saxony-Anhalt, the Prignitz and Uckermark areas of northern Brandenburg, as well as whole Westphalia are usually considered to be part of the North German region.
Northern Germany has traditionally been a Protestant-majority region, especially Lutheranism, with the two northernmost provinces of Schleswig-Holstein and Niedersachsen having the largest percentage of self-reported Lutherans in Germany. Exceptions are the Catholic districts Emsland, Cloppenburg and Vechta in the west, traditionally linked to the Catholic region of Westphalia in the south, and the southernmost part of Niedersachsen around the city Duderstadt, traditionally being part of the Catholic enclave region Eichsfeld.