Sudargas is a township in top north-western Suvalkija, ca. 35 km north-west of Šakiai and close to the border with what was East Prussia. In World War One, in the final clearing of Russian armies from East Prussia, Sudargas was taken by 31. Infanterie-Division on February 8, 1915.

After the German withdrawal from Russia at the end of 1918, Sudargas was not affected by further hostilities.

It is not clear whether Sudargas had previously had a czarist postal facility, but a Lithuanian postal branch, possibly an agentūra, was set up in 1921. So far, no other early details are available.

Sudargas was provided with Fourth Berlin Issue, Kaunas Colour printings, the Sėjėjas Issue etc. For cancelling, Sudargas made use of a makeshift two-line cachet with thin lines above and below, showing place and date. No other provisional markings have been reported.

A standard calendar-type postmarker (spelled SUDARGAS or SUDARGAI ?) was supplied ca. mid-1921.

Known provisional markings:

Cancelling by two-liner cachet:
21. 4. 1921 pair, Kaunas Colour 40 [colln. Liesis]
21. 4. 1921 single, Kaunas Colour 40 [colln. Doniela]
10. 5. 1921 singles, Berlin IV 1a, 1a [colln. Liesis]