Monsanto Chemical Works of Saint Louis, Missouri, was founded in 1901 by John Queeny and named for his wife, Olga Monsanto. The company’s first commercially successful product was saccharin, followed shortly thereafter by refined caffeine, vanillin, and aspirin. Within thirty years, largely under the influence of Queeny’s son Edgar, Monsanto Chemical Works expanded its business and product portfolio to include a number of manufacturing facilities in both the United States and abroad. In 1933, the company was renamed Monsanto Chemical Company.

By the late 1940s and well into the 1960s Monsanto Chemical Company introduced to industry several highly innovative products. Great strides were made in the areas of oil drilling and refining, plastic, silicon, synthetic rubber, lacquers, resins, adhesives, explosives, fine pharmaceuticals, food preservatives, crop protection, and atomic energy research. A separate Agricultural Division was created in 1960. To reflect the company’s progression into areas other than chemical production, in 1964 the company was again renamed Monsanto Company.

By the end of the 1960s and throughout the 1970s, Monsanto – encouraged by the public’s demands for safe, sophisticated, and efficient consumer goods coupled with the Federal Governments’ increased involvement with ecological legislation – focused its attentions on environmentally acceptable products and manufacturing processes. Products introduced during this time included polyesters and nylon-derivative textiles, electronic components to monitor and control factory emissions, safety fluids for heat fatigue and fire-suppression, fuel additives, light-weight and inexpensive plastics, structural safety glass for automotive and architectural applications, soybean-based protein alternatives for the health conscious, and nonnutritive sweeteners.

In the early 1980s, the all-encompassing term biotechnology was eagerly embraced by Monsanto to describe its research activities and subsequent manufacturing advances in the plant and animal sciences for the purpose of increasing food production and developing pharmaceutical products.

Many changes occurred at Monsanto in the 1990s. The plant biotechnology assets of Agracetus and an interest in Calgene, another biotech research company, were acquired, and purchase of the DeKalb Genetics Corporation was completed. Products introduced included Roundup Ready soybeans, cotton, and corn, as well as Bollgard insect-protected cotton. In 1997 the Industrial Chemical and Fibers divisions became a separate company, Solutia Inc. Also in 1997, Monsanto purchased Holden’s Foundation Seeds L.L.C. and Corn States Hybrid Service L.L.C.

A merger with Pharmacia Corporation in 2000 placed agricultural work into a subsidiary known as Monsanto, which became a separate company in 2002. Pharmacutical work remained with the Pharmacia Corporation, which became a subsidiary of Pfizer in 2003. As of 2009, Monsanto focused exclusively on agricultural work, with two main divisions: Seeds and Genomics, and Agricultural Productivity.

In 2016 Monsato and Bayer enter into a binding merger agreement, leading to the purchase of the company by Bayer. The name "Monsanto" is discontinued in 2018, and opperations in St. Louis transition to using the Bayer name. (https://www.bayer.com/en/history/2010-2022)