When Bavaria joined greater Germany in 1871 one of the conditions of the deal was the adoption across the whole country of the Bavarian Beer Purity Order – known popularly but incorrectly as the Reinheitsgebot. This brought largely unintended homogeneity to German brewing, which had previously being quite regional in its approach.
It would be lovely to believe that the Purity Order was brought in for the protection of consumers, but it was more to protect Bavarian brewers from an influx of “impure” competition and improve their prospects for sales across a much larger market. In practice, the Order was not fully imposed until 1906, and then breached again in 1919. Either way, it is seen, rightly or wrongly, as having had the effect of outlawing a number of local beer styles, especially from northern and eastern Germany.
In practice, a number these survived, either due to local quirks in the law, or else in the popular memory and the loyalty of home-brewers. Examples of these include Berliner Weisse, Gose and Lichtenhainer.
One beer from the north of Germany remains rare, and is hard to categorise.
Possibly originating in Dortmund, but definitely from northern Germany, this strong, dark ale style (8-11% ABV) has similarities with some of the strong stock ales once found in the UK, and the oak-aged ales of Belgium. Typically a little smoky, and definitely aged in oak for a time, it has a mild lactic edge. Its demise coincided with the rise in popularity of lagered Bockbier, though a few examples have started to re-appear again in its home country.