The Main metropolis was first mentioned on 22 February 794 in a document of Charlemagne for the Regensburg monastery, St. Emmeram. However, there is proof that the cathedral hill has been under continuous settlement since as early as 3000 BC. At the same place, a Roman military camp was established around 83 AD and in the Merovingian era, the court of a Franconian king. In 843, Frankfurt became at times the most important royal palatinate of the Eastern Franconians and the site of parliaments. In 1220, Frankfurt became a free imperial city. From 1356 onwards, the Golden Bull declared Frankfurt as the permanent city of choice for the Roman kings.

From 1562, the Emperor was also crowned in Frankfurt, the last one being the Habsburg Franz II. After the end of the Holy Roman Empire, Frankfurt joined the Confederation of the Rhine and under the First Prince Karl Theodor of Dalberg, became the capital of a short-lived (1810-1813) grand duchy of Frankfurt. In 1815, Frankfurt became a free city and the seat of the federal government.