The heart of what is now Leverkusen was a village called Wiesdorf, which dates back to the 12th century. The entire area was rural until the late 19th century, when industry prompted the development that led to the city of Leverkusen, and to its becoming one of the most important centres of the German chemical industry.
The chemist Carl Leverkus, looking to build a dye factory, chose Wiesdorf in 1860. He built a factory for the production of artificial ultramarine blue at the Kahlberg in Wiesdorf in 1861, and called the emerging settlement "Leverkusen" after his family home in Lennep. The factory was taken over by the Bayer company in 1891; Bayer moved its headquarters to Wiesdorf in 1912. After asset confiscation at the end of WWI it became IG Farben. The city of Leverkusen proper was founded in 1930 by merging Wiesdorf, Schlebusch, Steinbüchel and Rheindorf, and was posthumously named for Carl Leverkus. The IG Farben factories were bombed by the USAAF Eighth Air Force on December 1, 1943, by the RAF on August 22, 1943, and by the RAF during bombing campaigns on November 19/20 and December 10/11, 1943.
In 1975, Opladen (including Quettingen and Lützenkirchen since 1930), Hitdorf and Bergisch Neukirchen joined Leverkusen. The present city is made up of several villages, originally called Wiesdorf, Opladen, Schlebusch, Manfort, Bürrig, Hitdorf, Quettingen, Lützenkirchen, Steinbüchel, Rheindorf and Bergisch-Neukirchen.