Regensburg becomes a Free Imperial City in 1245 and is a trade center before the shifting of trade routes in the late Middle Ages.

At the end of the 15th century in 1486, Regensburg becomes part of the Duchy of Bavaria, but its independence is restored by the Holy Roman Emperor ten years later.

The city adopts the Protestant Reformation in 1542 and its Town Council remains entirely Lutheran.

From 1663 to 1806, the cityis the permanent seat of the Imperial Diet of the Holy Roman Empire, which becomes known as the Perpetual Diet of Regensburg.

Thus, Regensburg is one of the central towns of the Empire, attracting visitors in large numbers.A minority of the population remains Roman Catholic, and Roman Catholics are denied civil rights ("Bürgerrecht"), but the town of Regensburg is not to be confused with the Bishopric of Regensburg.

Although the Imperial city adopts the Reformation, the town remains the seat of a Roman Catholic bishop and several abbeys.

Three of the latter, St. Emmeram, Niedermünster and Obermünster, are estates of their own within the Holy Roman Empire, meaning that they are granted a seat and a vote at the Imperial Diet (Reichstag).

Thus, there is the unique situation that the town of Regensburg comprises five independent "states" (in terms of the Holy Roman Empire): the Protestant city itself, the Roman Catholic bishopric, and the three monasteries mentioned previously.In 1803, the city loses its status as a free city, following its incorporation into the Principality of Regensburg.

It is handed over to the Archbishop of Mainz and Archchancellor of the Holy Roman Empire Carl von Dalberg in compensation for Mainz, which had become French under the terms of the Treaty of Lunéville in 1801.

The archbishopric of Mainz is formally transferred to Regensburg.

Dalberg unites the bishopric, the monasteries, and the town itself, making up the Principality of Regensburg (Fürstentum Regensburg).

Dalberg strictly modernizes public life.

Most importantly, he awards equal rights to Protestants and Roman Catholics alike.