Because I am reading the game files and the numbers you gave are wrong.
Between 1816 and 1822 there was a third governorate – the Governorate of Berlin [de] – comprising the urban district of Berlin, the city of Charlottenburg and the municipalities of Gesundbrunnen, Lichtenberg, and Stralau.
The main reason is that forming Prussia from Brandenburg is a natural progression in game.
The Northern March was split off in 965, however, large parts were again lost in the Great Slav Rising of 983, and the margravial title did not become hereditary until the time of Albert the Bear, another Saxon count from the noble House of Ascania, who established the Margraviate of Brandenburg in 1157. Most of the Margraviate's territory was incorporated into the new Province of Brandenburg, most notably the Mittelmark between the rivers Elbe and Oder and the Neumark region east of the Oder River. I got the 7.5% discipline boost, then the 5% boost from quality, then the 5% boost from offensive to get 123% discipline. Brandenburg's provincial capital alternated between Potsdam, Berlin, and Charlottenburg during its existence. What is your army tradition, stability, and legitimacy? The remaining territory became part of the Soviet occupation zone and was transformed into the state of Brandenburg, with Potsdam becoming state capital. Be smart about what provinces you take and develop liberally, you'll be surprised about how far you can get with 25 provinces. The province comprised large parts of the North German Plain, stretching from the Elbe river in the west to beyond the Oder in the east, where the Neumark region bordered on the Prussian Grand Duchy of Posen (Province of Posen from 1848).
Emperor Charles IV by the Golden Bull of 1356 confirmed the electoral dignity of the Brandenburg margraves and in 1373 assigned the electorate to his son Wenceslaus in 1373.
And rinse and repeat. However, the Altmark on the western bank of the Elbe was incorporated into the Prussian Province of Saxony.
For a better experience, please enable JavaScript in your browser before proceeding. Keep in mind you'll get more MIL points on average than other countries, you can keep militarization up between teching and even ideas up to a size of 25-30 provinces.
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Other neighbouring provinces were Pomerania in the northeast, Silesia in the southeast, and Prussian Saxony in the southwest. For official use only. Larger towns were the royal residence Potsdam and the regional capital Frankfurt (Oder), furthermore Landsberg (present-day Gorzów Wielkopolski) in the east, the historic capital Brandenburg an der Havel as well as Cottbus, Forst and Guben (Gubin) in Lower Lusatia.
I started a new custom nation with console just to give an example of the provinces cap. Xsolla is an authorized global distributor of Paradox Interactive, EUIV: AAR's, Let's Plays, and Fan Fiction, EU IV: Alternate History Short Story Contest Contr.