NASSAU, a territory of Germany, now forming the bulk of the government district of Wiesbaden, in the Prussian province of Hesse-Nassau, but until 1866 an independent and sovereign duchy of Germany. It consists of a territory, 1,830 sq.m. in area, divided into two nearly equal parts by the river Lahn and bounded on the south and west by the Main and Rhine, on the north by Westphalia and on the east by Hesse. The southern half is almost entirely occupied by the Taunus mts., while to the north of the Lahn is the barren Westerwald. The valleys and low lying districts, especially the Rheingau, are very fertile, produc ing abundance of grain, flax, hemp and fruit ; but by far the most valuable product of the soil is its wine. Nassau is one of the most thickly wooded regions in Germany, and its forests yield good timber and harbour large quantities of game while the rivers abound in fish. There are upwards of a hundred mineral springs in the district; the best known are those of Wiesbaden and Ems. Other mineral wealth of Nassau includes iron, lead, copper, build ing stone, coals, slate, a little silver and a bed of malachite. Manu factures are unimportant, but brisk trade is carried on by rail and river in wine, timber, grain and fruit. There are few places of importance besides the above-named spas; Hochst is the only manufacturing town. Wiesbaden is the capital of the government district as it was of the duchy.
History.--LDuring the Roman period the whole of the district of Nassau was occupied by the Mattiaci and later by the Alamanni. The latter were subdued by the Franks under Clovis at the end of the 5th century, and at the partition of Verdun in 843 the country became part of the East Frankish or German kingdom. Christi anity seems to have been introduced in the 4th century. The founder of the house of Nassau is usually regarded as a certain Drutwin (d. 1076), who built a castle on a hill overlooking the Lahn, near the present town of Nassau. Drutwin's descendant Walram (d. 1198) took the title of count of Nassau, and placed his lands under the immediate suzerainty of the German king; previously he had been a vassal of the archbishop of Trier. Then in 1255 Walram's grandsons, Walram and Otto, divided between them their paternal inheritance, which had bee,n steadily increasing in size. Walram took the part of Nassau lying on the left bank of
the Lahn and made Weisbaden his residence; Otto took the part on the right bank of the river and his capital was Siegen. The brothers thus founded the two branches of the house of Nassau.
The fortunes of the Ottonian, or younger line, belong mainly to the history of the Netherlands. William the Silent, the best known of this line, and his descendants were called princes of Orange-Nassau, and this line became extinct when the English king William III. died in 1702. The descendants of Count John, his brother, remained rulers of Nassau until 1806, when the reigning prince, William VI., was deprived of his lands because he refused to join the Confederation of the Rhine. Some of them were given in 1815 to the other main line of the family, the one descended from Count Walram. In 1815 William VI. became king of the Netherlands as William I., and was compensated for this loss by the grant of parts of Luxemburg and the title of grand duke. When in 1890 William's male line died out Luxemburg, like Nassau, passed to the descendants of Count Walram. In the female line he is now represented by the queen of the Netherlands.
The territories possessed by the other branch of the house of Nassau were partitioned several times, and only in 1816 was the whole of Nassau united under the rule of Frederick William of Nassau-Weilburg as duke of Nassau. In 1866 Duke Adolph espoused the cause of Austria, sent his troops into the field, and asked the landtag for money. This was refused; Adolph was soon a fugitive before the Prussian troops, and on Oct. 3, 1866, Nassau was formally incorporated with the kingdom of Prussia.
For the history of Nassau see Hennes, Geschichte der Graf en von Nassau bis 1255 (Cologne, 1843) ; von Schutz, Geschichte des Herzogtums Nassau (Wiesbaden, 1853) ; von Witzleben, Genealogie und Geschichte der Fiirstenhauses Nassau (Stuttgart, 1855) ; F. W. T. Schliephake and K. Menzel, Geschichte von Nassau (Wiesbaden, 1865-89) ; the Codex diplomaticus nassoicus, ed. K. Menzel and W. Sauer (1885-87) ; and the Annalen des Vereins fur nassauische Alter tumskunde und Geschichtsforschung (1827 f.).