It arose from the first partition of Mecklenburg after the death of Henry Borwin II in 1227.

[1] It was named after the castle and settlement of Rostock and held the territories of Kessin, Kröpelin, Doberan, Ribnitz, Marlow, Sülze and Tessin in the modern German Bundesland (Federal State) of Mecklenburg-Vorpommern.

The first Fürst (prince) of Rostock was Henry Borwin III from the House of Mecklenburg (Obodrites); the last was his grandson Nicholas I "das Kind" (the child).

Already by 1311 Henry II, Lord of Mecklenburg sought to take the town of Rostock once more, and succeeded on 15 December 1312.

In 1312 the town of Rostock already saw Henry II as a representative of the Danish King.