Masurians are mostly descendants of colonists from Mazovia, but many of them have their roots in Germany, Lithuania, France, Austria, Scotland, the Netherlands and Russia.

Like most of the East Prussian population, they favored Protestantism and adopted Lutheranism in 1525 when Albert, Duke of Prussia secularized the duchy and converted.

Conclusion of the war and ensuing resettlements saw an ethnic conflict between leaving Masurians and incoming Kurpie mainly on religious (Protestant–Catholic) grounds.

The small minority of Protestant Masovians in southern Catholic Masovia inside Poland emigrated later to Prussian Masuria.

[4] Masurians showed considerable support for the Polish uprising in 1831, and maintained many contacts with Russian-held areas of Poland beyond the border of Prussia, the areas being connected by common culture and language; before the uprising people visited each other's country fairs and much trade took place, with smuggling also widespread.

[4] During the 1840s, the folklorist Gustaw Gizewiusz (Gustav Gisevius) collected Masurian folk songs which were later included in Oskar Kolberg's compilation Dzieła Wszystkie.

[4] Mother tongue of the inhabitants of Masuria, by county, during the first half of the 19th century: Before World War I many Masurians emigrated to the Ruhr Area, especially to Gelsenkirchen.

In all German geographical atlases published at the beginning of the 20th century, the southern part of East Prussia was marked as an ethnically Polish area, with the number of Poles estimated at 300,000.

[19] In general, popular resistance against linguistic Germanisation cannot be easily equated with anti-German sentiment or a strong attachment to the Polish national movement.

Most of Masuria's small Polish-speaking intelligentsia remained decisively pro-Prussian, often adhering to an older, multi-ethnic model of Prussian identity, centred on loyalty to their king, not so much on the German language.

[24] Richard Blanke summarised this long-standing attachment, going back to the late Middle Ages, as "Masurians became Prussian, in other words, before the Bretons (not to mention the Alsatians) became French.

[29] Kossert admits irregularities during the referendum, but asserts that in general, its results truthfully reflected the overwhelmingly pro-German sentiment in southern East Prussia.

[39] In 1943, "Związek Mazurski" was reactivated secretly by Masurian activists of the Polish Underground State in Warsaw and led by Karol Małłek.

[18] Speculations about the reasons of this emigration vary, from the economic situation and the undemocratic – communist – system in Poland[18] to the shrinking prospect of a return of Masuria to Germany.

[28] A group of Masurians migrated south and became one of the main components of the Lasowiacy, who live in the northern part of the Subcarpathian Voivodeship.