Angostura Bitters is a staple ingredient in many cocktails such as the Old Fashioned, Daiquiri, Manhattan and several Martini variants. It's rarely consumed neat and is mainly used to add flavour to cocktails, long drinks and occasionally to food. It's made in Port Spain, Trinidad by House Angostura who have been trading there since 1875. Angostura Bitters is comprised of ethanol, water, Gentian, spices and herbs although the exact recipe is a well guarded secret that is passed down through the generations with only one person at a given time knowing the entire recipe.
Angostura was first distilled in 1824 by Johann Gottlieb Benjamin Siegert; a German who was appointed as the surgeon general in Simon Bolivar's army stationed in Venezuela. Bolivar was an aristocrat who was instrumental in founding the various South American countries as independent states autonomous of Spain's monarchy. Angostura was made using local ingredients and it's speculated that Siegert was probably aided by the knowledge of the indigenous tribes people in this regard.
By 1830 Siegert had a distillery built for the creation of the bitters which was now being sold commercially. This was based in a town called Angostura and is how the bitters got its name; the town is now named Ciudad Bolivar. By 1857, Angostura Bitters was being sold internationally and in 1875 production was moved to Trinidad after the death of Siegert in 1870. Angostura was one of the few bitters to survive the American Prohibition and it has enjoyed a renewed popularity since the recent cocktail resurgence has increased demand for it.