Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online.Nassau was a German state within the Holy Roman Empire and later in the German Confederation. Its ruling dynasty, now extinct in male line, was the House of Nassau.Nassau, originally a countship, emerged on the lower Lahn River in what is today Rhineland-Palatinate. The town of Nassau was founded in 915. Robert, son of Count Dudo-Henry of Laurenburg, who had held Nassau as a fiefdom granted by the Bishopric of Worms, built a castle here about 1125, calling himself "Count of Nassau". Nevertheless this title was not acknowledged by the Bishop of Worms until 1159 under the rule of Robert''s son Walram.