#Borders this week goes to Petsamo, a Finnish province that only existed between 1921 and 1922.
The area had to be ceded by the Russian Soviet Federative Socialist Republic to Finland in 1921 as a result of the Treaty of Tartu, and the following year it was merged with the province of Oulu. In 1939, with Petsamo having become a part of the new province of Lapland, the area was occupied by the Soviet army, which left already in 1940 as part of the Moscow peace agreement. However, in 1944 Finland returned Petsamo again to the Soviet Union.
The Kansallisarkisto holds a map from the early 20th century – as you can see a very fragmented area not only in its political geography but in its physical one: http://www.archivesportaleurope.net/ead-display/-/ead/pl/aicode/FI-1/type/fa/id/VAKKA-276241.KA/dbid/C375613621/search/0/Petsamo