[4] From the Union of Lublin (1569) to the Partitions of Poland, there was no Polish-Lithuanian border, as both countries were a part of a single federated entity, the Polish–Lithuanian Commonwealth.

It was planned to create a security belt within a radius of 20 km from the border, from which all national minorities would be removed and repopulated with repatriates.

In Suwałki County, the District Plenipotentiary for delimitation stated that Lithuanians living in the areas which were annexed to Poland were hostile to the authorities and should be removed abroad.

However, the local authorities determined the final shape of the border and belonging of individual villages or their fragments for more than a year and a half.

1789 to 1987), leaving on the Polish side the following settlements: Pozasko, Budwiec, Markiszki, Hołyny, Rachelany, Burbiszki, Borysówka, Poluńce, Berżniki, Wołyńce, Krejwiany, Trompoliszki, Wojciuliszki, Jegliniec, Budzisko, Majdan, Kopowo, Smolnica, Poszeszupie, Butowszczyzna, Krejwiany, Ejszeryszki, Wilkupie, Olszanka Stakuny, Burniszki, Grzybina and Gromadczyna and an island on Lake Gałdauś.

The following settlements remained on the Lithuanian (then part of the Soviet Union) side:[10] Helenowo, Ustronie, Podbuwieć, Subacze, Kuciony, Okmiany, Kalwiszki, Tarnówka, Barwisze, Uździenniki, Gralińce, Bielańce, Kibarty, Polance, Buraki, Olkszniany, Giłujsze, Trompole, Zegaryszki, Grungliszki, Durpiej, Czarna Buda, Wołkowizna, Kamionka, Rykosieje, Lubowo, Nowosady, Barwisze, Wartele, Auksztokalne, Ogliniszki, Poszyrwinty, Misiszki and Okszyszki and two islands on Lake Gaładuś.

The border has since remained identical during the Soviet occupation of the Baltic states as well as after the restoration of the independence of Lithuania on 11 March 1990.

[11][12][13] On 5 March 1996, both countries signed a treaty on the common border, confirming its status and demarcation, as well as agreeing on the technical cooperation.

It is a flat narrow piece of land, a gap, that is between Belarus and Russia's Kaliningrad exclave and that connects the three NATO-member Baltic States to Poland and the rest of NATO.

[18][19][20] A July 2017 NATO exercise was for the first time focused on defense of the gap from a possible Russian attack,[18] and used troops and materiel from US, British, Polish, Lithuanian and Croatian sources.