oman relics have been found in the area of Gaggenau, and at the boundary between Oberweier and Winkel, the remains of walls and parts of an old "villa rustica" or Roman farm were discovered. This dates inhabitation of the area to between 80 and 260 AD. The first believed documentation of the area is 1243: however this cannot be confirmed as the source document is a copy of the original land title which has never been found. The title describes the separation of Gernsbach and Rotenfels by the Bishop of Speyer. Gernsbach was made an independent parish in this document. Until the discovery of this document, researchers believed that a document dated 1288 was the first mention of the town. Two finds, one in 1936 and one in 1956 of a considerable number of buried coins in the area, dating from the middle of the 13th century, lead us to believe that wealthy people were residing in the area at that time. In 1535 the Margraviate of Baden was divided and Gaggenau was allocated to the Upper Margraviate with its seat in the city of Baden- Baden. Following the break in the B Baden-Baden line in 1771 both of these areas were reunited. In 1617, one year before the start of the Thirty Years War, the population of Gaggenau was 400: by the time the wars had ceased the population of the town had dropped to less than 160.
1681 marks the start of industry in the town and in that year Margrave Ludwig Wilhelm founded a hammer factory in Gaggenau. This factory is the forerunner of the "Eisenwerke" or
iron processing factory, which is the ancestor of the modern day, "Gaggcnau-Werke". Two years following this, the town was to acquire its own school teacher but it wasn't until 1752 that the town had its own school. As with the other towns and villages in the area, the late 1600's were to bring disaster. In 1691 on the 26th of November, French troops attacked, burnt and pillaged the town. The "Maria Hilf" church (located in Moosbronn), a renowned church of pilgrimage, was consecrated in 1749.
1772 marks another important date in the history of Gaggenau's industry. It was in that year that a "Glashuettenbetrieb" (glass factory) was moved to the town and from that date until its closure in 1911, the factory produced fine glassware which included windows and scientific devices.
In 1839 the first postal station was established in Gaggenau and 20 years later the first telegrams began reaching the town. Telephone service to Gaggenau was set up in 1900.
Automobile construction first began in the town in 1893 with the establishment of the "Sueddeutsche Automobilfabrik". This company was purchased by Benz in 1910 and in 1926 Benz and Daimler entered into partnership. The world's first Diesel truck was developed in Gaggenau in 1922.
World War II saw the destruction of much of the old industrial parts of the town as the manufacturing plants were natural targets for the bombers. Where once large factories stood, there is now park land.