Island, Estonia. The largest of the islands in the Muhu archipelago, which divides the Baltic Sea from the Gulf of Riga, Saaremaa has an area of 1,031 sq mi (2,671 sq km). It was occupied in the 13th century by the Livonian Knights and was ruled successively by Denmark, Sweden, and Russia before becoming part of Estonia in 1918. In 1940 Estonia was incorporated into the U.S.S.R., and the island passed into the Soviet sphere. Saaremaa was occupied by German troops during World War II. In 1991 Estonia became an independent nation, and Saaremaa was once again an Estonian possession. Economic activities include agriculture, livestock raising, and fishing.