Province of Silesia in the context of Lower Silesia Province (Prussia)

The Frontier March of Posen–West Prussia (German: Grenzmark Posen-Westpreußen; Polish: Marchia Graniczna Poznańsko-Zachodniopruska) was a province of Prussia that existed from 1920 (de facto) and 1922 (de jure) until its dissolution in 1938. It comprised most of the former territory of West Prussia and parts of the Province of Posen that had remained within Germany following the territorial losses to the Second Polish Republic after the Greater Poland Uprising, and confirmed by the Treaty of Versailles. The province was created in 1922 as part of the Free State of Prussia within Weimar Germany, incorporating three remaining non-contiguous territories of the former provinces of Posen and West Prussia.

Schneidemühl (present-day Piła) served as the provincial capital. From 1934 onwards, the province came under the de facto administration of the Province of Brandenburg, and on 1 October 1938, the territory was officially dissolved by Nazi Germany. Its lands were subsequently incorporated into the neighbouring provinces of Pomerania, Brandenburg and Silesia. Following the end of World War II and the redrawing of borders, the entire area of the former province was incorporated into Poland, lying east of the Oder–Neisse line.

The Province of Lower Silesia (German: Provinz Niederschlesien; Silesian German: Provinz Niederschläsing; Polish: Prowincja Dolny Śląsk; Silesian: Prowincyjŏ Dolny Ślōnsk) was a province of the Free State of Prussia from 1919 to 1945. Between 1938 and 1941 it was reunited with Upper Silesia as the Province of Silesia. The capital of Lower Silesia was Breslau (now Wrocław in Poland). The province was further divided into two administrative regions (Regierungsbezirke), Breslau and Liegnitz.

The province was not congruent with the historical region of Lower Silesia, which now lies mainly in Poland. It additionally comprised the Upper Lusatian districts of Görlitz, Rothenburg and Hoyerswerda in the west, that until 1815 had belonged to the Kingdom of Saxony, as well as the former County of Kladsko in the southeast.

The Province of Upper Silesia (German: Provinz Oberschlesien; Silesian German: Provinz Oberschläsing; Silesian: Prowincyjŏ Gōrny Ślōnsk; Polish: Prowincja Górny Śląsk) was a province of the Free State of Prussia from 1919 to 1945. It comprised much of the region of Upper Silesia and was eventually divided into two government regions (Regierungsbezirke) called Kattowitz (1939–1945), and Oppeln (1819–1945). The provincial capital was Oppeln (1919–1938) and Kattowitz (1941–1945), while other major towns included Beuthen, Gleiwitz, Hindenburg O.S., Neiße, Ratibor and Auschwitz, added in 1941 (the place of future extermination of Jews in World War II). Between 1938 and 1941 it was reunited with Lower Silesia as the Province of Silesia.