On August 1, 1863, businessman Friedrich Bayer and dye expert Johann Friedrich Westcott were founded in Barmen (today's part of Wuppertal, Germany) Founded a pigment manufacturing company. In 1865, the two men purchased shares in a coal tar dye factory in the United States and began an export business of intermediates. In 1876, a factory was established in Moscow. On July 1, 1881, the descendants of Bayer and Westcott established a joint venture called Friedrich Bayer and Partners Pigment Works AG. In 1883, the company started production at its factory in Fores, northern France.
In 1884, chemist Carl Duisburg began his work at Bayer. Under his leadership, Bayer chemists successfully produced groundbreaking inventions. In 1888, Bayer created a pharmaceutical division. In 1891, the company purchased land in Leverkusen to build a production base. In 1897, Dr. Felix Hofmann, a scientific researcher at Bayer, successfully synthesized pure chemical and stable acetylsalicylic acid. In 1899, aspirin was registered as a trademark for the first time and became a popular painkiller around the world. In 1912, the company moved its headquarters to Leverkusen.
In 1925, Friedrich Bayer Pigment Works merged with other companies to form the industrial group Pigment Industry AG. Leverkusen became the main production center for the industrial group Lower Rhineland Conglomerate. After World War II, the Allied forces seized the industrial group of Pigment Industry AG and later dismantled the company. In 1951, Bayer Pigment Works AG was re-established. In 1972, the company changed its name to Bayer Deutschland AG and rapidly developed into an international chemical and pharmaceutical group. In 1973, the Bronsbutel production base broke ground. The groundbreaking ceremony for the Monheim Crop Protection Center in Germany was held in 1979. In 1986, Bayer repurchased the rights to use the Bayer trademark in the United States from the American pharmaceutical company Sterling Druger. In 1988, the Medical Research Center held its inauguration ceremony in Westport, Connecticut, USA.
In the same year, Bayer became the first German industrial company to list its shares on the Tokyo Stock Exchange. Also that year, all Bayer activities in the United States were unifiedly managed by Bayer Management Holdings USA, located in Pittsburgh, Pennsylvania, USA. In 1989, Bayer purchased Cooper Technicon Company in Tower City, New York, USA, thus becoming one of the world's largest suppliers of diagnostic systems and clinical chemistry reagents. In 1990, Bayer acquired the Rubber Division of Nofa Company in Alberta, Canada, for DM 1.7 billion and renamed it Bowresa Rubber Company, with its headquarters in Toronto, Ontario, Canada. This acquisition makes Bayer the world's largest raw material producer in the rubber field. In 1991, the Bayer Exhibition and Exchange Center was opened in Leverkusen. In 1992, Bayer merged Mombai AG, Melers AG and Agfa AG with Bayer Management Holdings USA to form a new operating company named Mellas Corporation.
On February 27, 2014, Bayer Group announced the acquisition of all shares of Yunnan Dianhong Pharmaceutical Group.