The Wettin Elector John George I of Saxony stipulated in his will dated 20 July 1652 that his three younger sons should receive secundogeniture principalities.

Prince Christian, the third eldest son, received, among other properties, the estates of the former Bishopric of Merseburg, secularised in 1565: the castles, cities and districts of Merseburg, Plagwitz, Rückmarsdorf, Delitzsch (with Delitzsch Castle), Bad Lauchstädt, Schkeuditz, Lützen, Bitterfeld, Zörbig, the County of Brehna as well as the Margraviate of Lower Lusatia, including the cities and castles of Lübben, Doberlug, Finsterwalde, Döbern, Forst and Guben.

After the death of the last male heir of the Saxon branch line in 1738, the Duchy of Saxe-Merseburg fell back to the Electorate of Saxony.

These territories remained dependent on the main line and their sovereignty was severely restricted.

They were named after their owner's residences and disappeared with the death of their first duke, because none of them fathered surviving male heirs.