Unterwalden (ŏnˈtərväldən) [key], canton, central Switzerland, one of the Four Forest Cantons. A mountainous, forested, and chiefly pastoral region, Unterwalden is divided into the half cantons of Obwalden (1993 pop. 30,200), 190 sq mi (492 sq km), in the west, with its capital at Sarnen, and Nidwalden (1993 pop. 34,900), 106 sq mi (275 sq km), in the east, with its capital at Stans. Dairying and woodworking are the main occupations of Obwalden, while the economy of Nidwalden revolves around its winter tourist facilities. The population of Unterwalden is German-speaking and Roman Catholic. In 1291, Unterwalden formed with the cantons of Uri and Schwyz a league that became the nucleus of the Swiss Confederation (see Switzerland). The two half cantons officially split from each other in 1340, although generally they continued to act as one unit. They gained sovereign status as individual units in 1803.