The administrative region was bordered on the north by Regierungsbezirk Bromberg, to the west by the Province of Brandenburg, to the south by the Silesia Province, and to the east by Russian Congress Poland.
The Posen region was inhabited mainly by Poles practicing Roman Catholicism, although it had a minority of Germans, mostly Protestants.
Note: Prussian provinces were subdivided into units called Kreise (singular Kreis, abbreviated Kr., English "circle"), which were similar to large counties in US terms.
Cities would have their own Stadtkreis (English: "urban district") and the surrounding rural area would be named for the city, but referred to as a Landkreis (English: "rural district").
The administrative region of Posen had a majority Polish population, with a significant German minority who were mostly concentrated in the western districts.