A region of central and eastern Russia stretching from the Ural Mountains to the Pacific Ocean. Inhabited by a variety of peoples including the Ostyak, Chukchi, Evenki, and Yakut, Siberia was annexed by Russia in stages during the 1500s and 1600s. Long used as a place of exile for political prisoners, Siberia began to be developed for its mineral resources after the completion of the Trans-Siberian Railroad in the early 20th century.