The monarch of the Duchy was the Prussian King (a Hohenzollern) and his representative was the governor-general: the first was Duke Antoni Radziwiłł (1815-1831), married to Princess Luiza of Prussia, the king's cousin. The governor was assigned to give advice in matters of Polish nationality, and had the right to veto the administration decisions, in reality however all administrative power was in the hands of Prussian over-president of the province.
The territory of the duchy was divided into 2 districts: Poznan District, Bydgoszcz District, and 26 counties administered by the landrats and the county councils. In 1824 the Duchy also received the provincial council (term started in 1827) but with little administrative power reduced only to advice matters.
Up to 1830 the Prussian authorities were relatively tolerant to the Polish people, only the Prussian administrative schemes were introduced and the role of German language was strenghened in education.
After the November Uprising (1830 in Congress Poland against Russia) which was significantly supported by the Poles from the Grand Duchy of Poznan, the Prussian administration under over-president Edward Flotwell introduced a system of police and repression against the Poles. He started to expel the Poles from administration, tried to weaken the Polish nobility by buying its lands, and after 1832 the role of the Polish language in education was significantly supressed.
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After 1846 it was renamed to Provinz Posen.
See also:
Repression system after 1830
Milder period after 1840