The city adopted the Protestant Reformation in 1542, and its Town Council remained entirely Lutheran until the incorporation of the city into the Principality of Regensburg under Carl von Dalberg in 1803.
It was an important camp on the most northern point of the Danube: it corresponds to what is today the core of Regensburg's Altstadt ("Old City") east of the Obere and Untere Bachgasse and West of the Schwanenplatz.
It is believed that even in late Roman times it was the seat of a bishop, and St Boniface re-established the Bishopric of Regensburg in 739.
The first settlements in Regensburg date to the Stone Age.
The Celtic name Radasbona was the oldest name given to a settlement near the present city.
Dalberg united the bishopric, the monsteries and the town itself, making up the Principality of Regensburg (Fürstentum Regensburg). Most importantly he awarded equal rights to Protestants and Roman Catholics alike.
In 1810 Dalberg ceded Regensburg to the Kingdom of Bavaria, he himself being compensated by the towns of Fulda and Hanau being given to him under the title of "Grand Duke of Frankfurt".
Thus Regensburg was one of the central towns of the Empire, attracting visitors in large numbers. It was 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 was formally transferred to Regensburg.
1: The Bishopric of Regensburg acquired Reichsfreiheit around the same time as the City.
Of the three Imperial Abbeys in Regensburg, Niedermünster had already acquired Reichsfreiheit in 1002, St.
Between April 19 and April 23, 1809, Regensburg was the scene of the Battle of Ratisbon between forces commanded by Baron de Coutaud (the 65th Ligne) and retreating Austrian forces.