The elder brother of the philosopher Friedrich Heinrich Jacobi, Johann Georg was born at Pempelfort near Düsseldorf.

From 1774 to 1776, Gleim and Jacobi edited Iris, to which Goethe, Heinse, Lenz, and Sophie La Roche were contributors.

The city's Catholic population and the teaching staff considered this a provocation, but Joseph was known for his erratic acts of forced Enlightenment.

This happened again in 1803 during Napoleonic domination of the Breisgau when Jacobi's excellent knowledge of French helped to overcome differences with the authorities.

Following Napoleon's defeat Freiburg and the Breisgau were not restored to the Habsburgs but remained under the rule of the Grand Duchy of Baden.