Under the reign of Charles, the consequences of the Thirty Years' War in the agricultural county could be overcome more quickly than they were in the more industrialized regions of the Holy Roman Empire.

Even before the Edict of Fontainebleau (October 1685), Charles adopted on 18 April 1685 the Freiheits-Concession [ "Freedom Concession" ],[1] promising the exiles from France, the Huguenots and Waldensians, free settlement and their own churches and schools.

In the following years, about 4000 the Protestants fled persecution in their homelands for Northern Hesse and, for example, about 1700 of them settled in Oberneustadt, the newly created borough of Kassel.

Landgrave Charles continued the design of the hillside park, Wilhelmshöhe ("William's Peak") in the Habichtswald ("Hawk Forest"), now a nature preserve west of Kassel.

After the Marquise de Langallerie, the next mistress and confidante was Barbara Christine von Bernhold (1690–1756), who rose to Großhofmeisterin ("Senior Mistress of the Court") under Charles's son William VIII and was raised to the rank of Reichsgräfin ("Imperial Countess") in 1742 by the Holy Roman Emperor Charles VII.