Aspirin, also known as acetylsalicylic acid, is a nonsteroidal anti-inflammatory drug used to reduce pain, fever, and/or inflammation, and as an antithrombotic. Specific inflammatory conditions that aspirin is used to treat include Kawasaki disease, pericarditis, and rheumatic fever. A precursor to aspirin found in the bark of the willow tree (genus Salix) has been used for its health effects for at least 2,400 years. In 1853, chemist Charles Frédéric Gerhardt treated the medicine sodium salicylate with acetyl chloride to produce acetylsalicylic acid for the first time. Over the next 50 years, other chemists, mostly of the German company Bayer, established the chemical structure and devised more efficient production methods.

Source: Wikipedia