Abbott’s Bitters is an extinct product.
It was made by the C.W. Abbott company in Baltimore, Maryland from 1865 until around 1950.
It was one of the big three bitters sold in America, the other two being Angostura and Peychaud.
Abbott’s Bitters were barrel-aged. The recipe was changed sometime in the 1940s before production ended; purists say that it wasn’t as good after the change.
Abbott’s were considered the best bitters for a Manhattan (Angostura are used now.)
There are still some vintage bottles floating around at some home bars, as well as recipe booklets, and Abbott’s-branded bar paraphernalia.
Enthusiasts try to approximate the bitters by using vodka, gentian, ginger, cardamom, cassia, cloves, sugar, then barrel aging the mixture.