1: The Old Swiss Confederation was not internationally recognised until after the Peace of Westphalia in 1648. In 1291, the two halves of Unterwalden were founding members of the Confederation.
2: Unterwalden never really existed as a single entity, usually being governed as the two half-cantons of Unterwalden ob dem Wald (Unterwalden over the woods, Obwalden) and Unterwalden nid dem Wald (Unterwalden under the woods, Nidwalden).