SIEGEN. zē′gen. A town in the Province of Westphalia, Prussia, situated on the river Sieg, 47 miles east by south of Cologne. It has two castles of the Princes of Nassau-Siegen. Siegen is an important iron centre, the vicinity abounding in iron, copper, lead, and zinc mines. In and about the town are numerous puddling and rolling mills, machine works, and paper, cloth, and leather manufactories. Siegen, formerly a possession of the Dutch branch of the House of Nassau, passed to Prussia in 1815. Population (commune), in 1890, 18,242; in 1900, 22,111.