Estonia's land border with Latvia runs 267 kilometers; the Russian border runs 290 kilometers. From 1920 to 1945, Estonia's border with Russia, set by the 1920 Tartu Peace Treaty, extended beyond the Narva River in the northeast and beyond the town of Pechory (Petseri) in the southeast. This territory, amounting to some 2,300 square kilometres (888 sq mi), was incorporated into Russia by Stalin at the end of World War II. For this reason the borders between Estonia and Russia are still not defined.
What document established the border between Russia and Estonia?
the 1920 Tartu Peace Treaty