Herbsaint is the last pastis manufactured in the United States. It is produced by the Sazerac Company, in New Orleans, based on the original formula of the Legendre family. Their formula dates from the halcyon days of absinthe consumption, the years following the French campaign in Algeria, when it was sold as "Legendre Absinthe".
The two other American pastis, Milky Way and Green Opal, never returned to production after Prohibition was repealed. Legendre Absinthe returned to production as Herbsaint, due to the laws of certain states of the US that ban any liquor called "absinthe" under the assumption that it contains thujone, from wormwood.
Herbsaint, which is pronounced "ab-sant", is a yellow liquor, and louches when it contacts water. The flavor is much less sweet than Pernod. It is absolutely essential to two of the cornerstones of New Orleans cuisine, the Sazerac cocktail and Oysters Rockefeller.
Historical information from www.herbsaint.com