After World War I, the governorate was split between the Second Polish Republic and Lithuania, mostly along ethnic lines (with an exception of the area in the proximity of Puńsk and north of Sejny).
[1] The Polish part, known as Suwałki Region, was incorporated into the Białystok Voivodeship.
According to contemporary Russian Empire statistics, from 1889 the Suwałki Governorate was predominantly Lithuanian since they comprised 57.8% of the population.
[2] Lithuanians formed a majority only in the northern part of the governorate in the counties of Kalvarija, Marijampolė, Naujamiestis, Vilkaviškis as well as the eastern part of the Sejny county.
[3][4] Before World War I, the Suwałki Governorate was economically the least developed area of Congress Poland.