Often identified as the oldest, and also as one of the most successful, constitutional structures of autonomism in existence, the Åland Islands autonomy celebrated its centennial in 2022. Actually, the first Self-Government Act for the Åland Islands was enacted already in May 1920 by the Parliament of Finland, and according to Section 38 of the Act, it entered into force on 7 May 1920. Therefore, from a legal point of view, this fundamental law of the autonomy arrangement existed from that point on and was, in 2022, already 102 years old. However, around the turn of the decade 1910s/1920s, the inhabitants and especially the political establishment of the Åland Islands were seeking for secession from Finland and for incorporation and integration with Sweden. The Council of the League of Nations confirmed a Settlement between the two States that contained seven paragraphs aiming at the preservation of the Swedish character of the area. Therefore, in 1922, the Self-Government Act was complemented by the Guaranty Act, which transformed the seven paragraphs into the legal order of Finland. After more than 104 years, the constitutional structures of autonomism in the Åland Islands have been so successful that secessionism has practically disappeared as a political orientation among the inhabitants of the Åland Islands.