Having lost his mother soon after birth, Jacob from the age of two grew up with his relatives in Königsberg and Berlin. Jacob studied in Rostock, Leipzig, Amsterdam and Leiden and travelled around Europe. In 1639 he became Duke of Courland. His reign is justly considered as the time of prosperity of the Duchy. A large merchant fleet was created, more than 100 ships were built, construction materials were manufactured, sawmills, coopers’ workshops, mills, tar kilns, saltpetre breweries and paper mills were working. Crafts were flourishing and each branch had its outstanding craftsmen. Courland had two colonies – Tobago near South America and St. Andrews Island at the mouth of the River Gambia in Western Africa.
In Jacob’s marriage with Luise Charlotte nine children were born. The relationship of the dukes of Courland with the families of many rulers of European countries broadened. For example, the oldest son of Jacob’s daughter Maria Amalie and the prince of Hesse-Kassel became king of Sweden in 1720, and his successor in direct line is also the present King of the Netherlands, Willem-Alexander.
Courland was ravaged by the war between Poland-Lithuania and Sweden. In 1658 the Swedish troops captured Jelgava Palace and seized the Duke and his family and took them to Russia. Only in 1660 did they return to the devastated Courland. Its renewal took much strength and resources.
Duke Jacob was buried in a pewter sarcophagus in the vault on September 21, 1682. Its restoration was completed and the burial was consecrated in 2010.