Historical region, Latvia. Located on the Baltic Sea, it was named for the Curonians, who had established a tribal kingdom there by the end of the 9th century. Conquered in the 13th century by the Livonians, in 1561 the area was incorporated into the duchy of Courland, which became a Polish fief. The duchy flourished during the 17th century with the development of industries and foreign trade. From 1737 its duke was a client of the Russian throne, and it came under Russian rule in 1795. It became part of the newly independent Latvia in 1918.