Ruled by a cadet branch of the Albertine House of Wettin, the duchy passed to the Electorate of Saxony upon the extinction of the line.

Therefore, upon his death the Duchies of Saxe-Zeitz, Saxe-Merseburg and Saxe-Weissenfels arose, the latter was granted to the second eldest son Augustus,[1] who already served as the Protestant administrator of the Archbishopric of Magdeburg since 1638, then residing at Halle.

By Querfurt, the ducal Saxe-Weissenfels line gained the status of an Imperial State (at times called Saxe-Querfurt) and member of the Upper Saxon Circle, though without a vote in the Reichstag.

According to legend it was Duke Johan Adolf I admiring George Frederic's performance on the church organ of Neu-Augustusburg Castle, who promoted his musical career.

In 1713 Johann Sebastian Bach dedicated his cantata Was mir behagt, ist nur die muntre Jagd, BWV 208 to Christian of Saxe-Weissenfels in celebration of the duke's 31st birthday, it was first performed at the ducal Neuenburg Castle at Freyburg.