In 1606 the Elector had a town fortress with a citadel erected from the village of "Mannenheim", founding the basis for the later town and residential palace.
The later Elector from the Catholic Palatinate-Neuburg line was at first Canon of Cologne, Salzburg and Mainz. Following his subsequent military career, he applied in vain for the crown of the Polish king in 1700. Beginning in 1705 he lived as the imperial governor in Innsbruck and inherited the electorship at the age of 55. In 1718 Carl Philipp moved to Heidelberg, where his regency was marked by conflicts with the reformed powers. For this reason he moved his residence to Mannheim Fortress in 1720, where he had a Baroque palace built.
Carl Theodor, who became an orphan at an early age, received an unusually thorough education for that time at the court of his uncle Carl Philipp in Mannheim. He learned five languages and pursued natural sciences, literature, art, history and theology. In addition, he played several musical instruments and perfected his skills in riding, fencing and dancing. The education of the future elector even included studies at the universities of Leijden and Leuwen.
In 1742 he married his cousin Elisabeth Augusta. In the same year he assumed the electorship following the death of this childless uncle. Carl Theodor kept a luxurious court with high expenditures. These also included the promotion of the arts. He founded a painting and sculpting academy, the Palatinate Academy of the Sciences (pfälzische Akademie der Wissenschaften), the Electoral German Society (kurfürstliche Deutsche Gesellschaft), which successfully supported German-language theater, and the National Theater.
When the last Bavarian Wittelsbach died, Carl Theodor was forced to assume the electoral inheritance in Munich. In 1777 he left the Palatinate residences.
The later Electress, Carl Philipp's granddaughter, was engaged to the then eleven year old Carl Theodor at the age of 14. She was artistically talented and cultivated a wide range of intellectual interests.
After 19 years of marriage a son was born in 1761 who, however, died in the same night as a result of the difficult birth. Elisabeth Augusta was unable to have any further children after this. However, the relationship to Carl Theodor had long been a tense one and their marriage had become unhappy after these events. Elisabeth Augusta retreated completely to her palace in Oggersheim, founded her own court there and pursued artistic interests. She was well loved among the population as a benefactress.
For political reasons, the hereditary prince of Baden was married to Napoleon's niece and adopted daughter, Stephanie de Beauharnais-Napoleon. Napoleon sought to establish family ties with several older European dynasties.
The marriage in 1806 between Karl and Stephanie was an unhappy one for many years. According to contemporary reports, Karl appears to have been a weak person with poor education. Under bad influence he at first continued his extravagant bachelor's life so that even Napoleon felt compelled to make an official complaint to his grandfather. Schwetzingen was assigned to the couple as its summer residence. However, as the two lived in separate places in the early years (he in Karlsruhe, Stephanie in Mannheim), only Grand Duchess Stephanie initially used the expansive gardens with her royal retinue.
The fate of Stephanie Louise Adrienne de Beauharnais was determined by the political upheavals of her age. Born in the year of the Revolution 1789, she had to be brought to safety in the wake of the reign of terror. As a relative of the new sovereign family, Napoleon's niece then unexpectedly came to the splendid environment of the French imperial Court. Napoleon included her in his dynastic policy of alliances and adopted her to marry her to Karl, the hereditary prince of Baden.
In the strange country and with the Grand Duke's family hostile toward her, she led an unhappy life for many years. She saw her main duty in caring for her daughter. The two sons died at a young age. Due to her diverse artistic and intellectual interests, her widow's seat in Mannheim became a modest but lively court in social demand. Over the course of time Stephanie became a recognized German sovereign, yet in her heart she had remained French.