Strasbourg remained a significant place through Merovingian and Carolingian times. In 842, amidst civil war among Charlemagne's three grandsons, the two younger brothers swore the Oaths of Strasbourg, promising to work together against their older brother Lothar. This is famous partly because Louis' men swore in proto-German, Charles' in proto-French, very important early texts in both languages. When the empire was partitioned, Strasbourg ended up in the portion of the older brother Lothar, for whom the region was called Lotharingia, from which the modern provincial name Lorraine derives.
The ruler of Strasbourg across the early Middle Ages was its bishop. There were at least two armed revolts against him, but he remained in charge down to 1262. In 1260 a new, very aristocratic bishop, Walter von Geroldseck, issued a Manifesto of Grievances against the townspeople, saying they were not respecting the bishop's authority or paying him all the taxes due to him. By then the booming town had a lot more money and men than the bishop, so their response was, "come and collect your taxes if you can." Walter called for help from his fellow lords and bishops and raised an army. It was a tense, roughly equal standoff until one of the lords who had come to help the bishop, Charles of Hapsburg, decided to switch sides and support the town. (Those wily Hapsburgs, at it again.)
Months of raiding eventually culminated in the Battle of Hausbergen. The bishop – he was the sort of bishop who commanded his own army, in full armor – thought he had caught the forces of the town at a disadvantage and ordered an immediate cavalry charge, but he was too far away and the townsmen had time to form up properly for defense. The bishop was killed and his men were so badly routed that the new bishop had to surrender all his claims over the town, which became an Imperial Free City.
The town was a key site in the early days of the Reformation, and in 1605 saw one of Europe's first daily newspapers. In 1681 it was conquered by the armies of Louis XIV, becoming part of France.