German monarch who succeeded to the ducal throne in infancy (1758), and passed his boyhood under the guardianship and regency of his mother, the Duchess Anna Amalia. Karl August took over the government in 1775, marrying Princess Luise of Hesse-Darmstadt in the same year. He invited Goethe to Weimar in 1775, at first as a boon companion, and then gradually entrusted more and more of the administration to him. The Duke, with Goethe as his adviser, ruled on enlightened principles, encouraging industry, including textiles and glass, and mining. He improved the educational facilities of the state, and inaugurated a botanical garden and an art museum. He rebuilt the Court Theatre (1791) and established a permanent company with Goethe as director. His great energy, and his interest in military affairs, which his little state could not satisfy, led to tensions and to absences in Prussia; his liaison with the principal actress, Caroline Jagemann, endangered both the theatre and his relationship with Goethe. Nevertheless, the mutual regard of the two men persisted in spite of occasional estrangement. Weimar during Karl August’s reign was the literary focus of Germany, attracting Wieland, Herder, and Schiller as well as Goethe, and becoming an indispensable place of call for the grand tour. In 1815 Karl August’s title was elevated to Grand Duke (Großherzog). He was one of the first German rulers to grant a constitution (1816).
He had seven children and is said to be the father of at least 38 illegitimate children. He died on 14 June 1828 at age 70 in Graditz, near Torgau, Province of Saxony.
Link to Wikipedia biography