The Palatinate line of the House of Wittelsbach was divided into four lines after the death of Rupert III in 1410, including the line of Palatinate-Simmern with its capital in Simmern. This line became extinct in 1685 with the death of Charles II. The House of Palatinate-Neuburg line inherited the Electorate.
The house of Palatine-Simmern, in the person of the 1st elector, Frederick III, were staunch Calvinists. Frederick III was a devout convert to Calvinism, and made the Reformed confession the official religion of his domain by overseeing the composition and promulgation of the Heidelberg Catechism. His support of Calvinism gave the German Reformed movement a foothold and base within the Holy Roman Empire. It was also part of the appeal of Frederick V to the Bohemians in electing him King.