A partnership between dye salesman Friedrich Bayer and master dyer Johann Friedrich Weskott brought about “Friedr. Bayer et comp.” to manufacture and sell synthetic dyestuffs. The production of these dyes from coal-tar derivatives had only been invented a few years previously, opening up a new field of business for the still-young chemical industry.
A scientific laboratory was built in Wuppertal-Elberfeld - which was also the company's headquarters from 1878 until 1912 - that set new standards in industrial research. Bayer's research efforts gave rise to numerous intermediates, dyes and pharmaceuticals, including the "drug of the century," Aspirin, which was developed by Felix Hoffmann and launched onto the market in 1899. It was during this time that the company gained an international presence, exporting as far abroad as China and maintaining subsidiaries in Russia, France, Belgium, the United Kingdom and the United States.
As time went on, the Elberfeld site proved to be too small for continuing expansion. For this reason, Bayer first purchased the factory of Dr. Carl Leverkus & Sons North of Cologne in 1891 before acquiring additional land along the Rhine River. Leverkusen became the company's headquarters in 1912.
After World War II, Bayer concentrated once again on research and development – as a foundation of the reestablishment of operations. Contributing to the company's expansion was the further development of polyurethane chemistry, new crop protection products, fibers such as the polyacrylonitrile fiber Dralon, the thermoplastic Makrolon, new dyestuffs for synthetic fibers and many other inventions. New products such as cardiovascular medicines, dermal antifungals and broad-spectrum antibiotics emerged from Bayer's pharmaceutical laboratories.
In 1988 Bayer celebrated the 125th anniversary of its founding. That same year, Bayer AG became the first German company to list its shares on the Tokyo Stock Exchange.
Bayer acquired the North American self-medication business of Sterling Winthrop in 1994 - a milestone in the company's history, as the purchase also allowed the company to regain the rights to the "Bayer"
company name in the United States. For the first time in 75 years, Bayer could operate in the United States under its own name and with the Bayer Cross as its corporate logo. In 1995 U.S.-based Miles Inc.
was renamed Bayer Corporation.
The year 2002 saw the listing of Bayer’s shares on the New York Stock Exchange, the world’s most important securities market, under the ticker symbol BAY. In the same year, on July 1, the Bayer Group began the biggest reorganization in its history, which has led to the current structure of the company.
In the year of 2003, the subgroups Bayer Chemicals AG and Bayer HealthCare AG and the service
company Bayer Technology Services GmbH gain legal independence as part of the reorganization of the Bayer Group. The subgroup Bayer MaterialScience AG and the service companies Bayer Business Services GmbH and Bayer Industry Services GmbH & Co. OHG follow in December.
In March, Bayer announces a public takeover offer for Schering AG, Berlin, Germany. In July, Bayer gains control of 92.4 percent of the approximately 191 million outstanding Schering shares. In December,
Schering AG is officially renamed Bayer Schering Pharma AG.
In 2005, Lanxess AG is spun off from the Bayer Group.
In 2006, Takeover of Schering AG, Berlin, Germany.
In 2013, Bayer will have its 150 year of celebration.
In 2014 ,Takeover of the Consumer Care business of Merck & Co., Inc., USA.
In 2015, Bayer MaterialScience became an independent company under the name of “Covestro” .
In 2016, Reorganization of the Bayer Group.