High Quality Content by WIKIPEDIA articles! The history of aspirin (also known as acetylsalicylic acid or ASA) and the medical use of it and related substances stretches back to antiquity, though pure ASA has only been manufactured and marketed since 1899. Medicines made from willow and other salicylate-rich plants date back at least to 400 BCE, and were part of the pharmacopoeia of Western medicine in Classical antiquity and the Middle Ages. Willow bark extract became recognized for its specific effects on fever, pain and inflammation in the mid-eighteenth century. Lewis and Clark allegedly used willow bark tea in 1803-1806 as a remedy for fever for members of the famous expedition. By the nineteenth century pharmacists were experimenting with and prescribing a variety of chemicals related to salicylic acid, the active component of willow extract.