In 853 Louis the German raised it to the rank of capital of the eastern portion of the French empire; extended its borders, and built the church of St. Saviour close to where the autumn fair was held, in accordance with the traders' custom of setting up their booths under the walls of churches and temples.
The custom of electing the emperor at Frankfort was begun by that great Swabian house whose name alone calls up a host of terrible and melancholy recollections. In 1240 Frederic II granted letters of safe conduct to all going to the market of Frankfort; and the Emperor Louis of Bavaria, wishing to show gratitude for his election, proved his attachment to the town by granting great advantages, among others the right of holding a fair for fifteen days during Lent, which was known as the Easter fair.
The Emperor Charles IV confirmed the right of the Imperial Election to Frankfort by the famous Golden Bull issued in 1356. This Bull provided the Emperor Napoleon with an opportunity for displaying his excellent memory. Dining one day with half a score of sovereign princes, at the meeting of Erfurth, the conversation chanced to turn on the Golden Bull, which, until the Confederation of the Rhine, had laid down the rules for Imperial elections. The Prince Primate, being on his own ground, gave some details concerning the Bull, fixing the date for 1409.
"I think you are mistaken, prince," said Napoleon. "If my memory is correct, the Bull was published in 1356 in the reign of the Emperor Charles IV."
"Your Majesty is right," said the primate, reconsidering, "but how is it you remember the date of a bull so exactly? Had it been a battle it would be less wonderful."
"Shall I tell you the secret of this wonderful memory, prince?" enquired Napoleon.
"Your Majesty would give us all much pleasure."
"Well," continued the emperor, "you must know that when I was a sub-lieutenant in the Artillery—"
Whereupon there was so decided a movement of surprise and curiosity among the illustrious guests that Napoleon paused an instant, but seeing that all were waiting for him to continue, he resumed with a smile:
"I was saying that when I had the honour of being a sub-lieutenant of Artillery I was in garrison at Valence for three years. I did not care for society, and lived very quietly. By a lucky chance I had rooms opposite a well-read and obliging bookseller, whose name was Marcus Aurelius, and who gave me the run of his library. I read and re-read everything in his shop two or three times during my stay in the capital of the Drôme, and I remember everything I then read—even to the date of the Golden Bull."