It extends roughly 290 km (180 mi) eastwards from the lower Vistula River to the Poland-Lithuania border and occupies an area of roughly 52,000 km² (20,000 sq mi). Administratively, the lake district lies within the Warmian-Masurian Voivodeship. Small parts of the district lie within the Masovian and Podlaskie Voivodeships.
The lake district was shaped by the Pleistocene ice age. Many of its hills are parts of moraines and many of its lakes are moraine-dammed lakes. The lakeland was successively part of the monastic state of the Teutonic Knights, the Duchy of Prussia, and the Prussian province of East Prussia. While part of the German Empire, it was the location of the First Battle of the Masurian Lakes (1914) and the Second Battle of the Masurian Lakes (1915) during World War I. In 1945 after World War II, it was placed under Polish administration according to the Potsdam Agreement.