The St. Charles Sister Cities Program was incorporated in 1994. The mission of the program is to encourage and implement high quality programs that foster mutual understanding, friendship, and goodwill through cultural, social, business, and educational exchanges between St. Charles and her Sister Cities.
Currently, St. Charles' only Sister City is Ludwigsburg, Germany. It was selected because:
- It is comparable in size to St. Charles and located near a larger city, Stuttgart, which is a Sister City to St. Louis, and also across the Neckar River from Marbach, a Sister City with Washington, Missouri.
- It was seeking an American city as its fourth Sister City, hoping to complete the cycle of partnerships with communities in each of the four Allied countries that were Germany's opponents during World War II.
- An American Army base (Pattonville) had been located just outside Ludwigsburg from 1946-1993. A good relationship existed between the soldiers and the citizens, and Ludwigsburg was looking for a way to continue its American contacts.
- Correspondence with Ludwigsburg City officials in 1993 brought an invitation from then-Lord Mayor (Oberbuergermeister) Hans Jochen Henke to then-St. Charles Mayor Grace Nichols and Joe Daues to visit the German community.