Shrubs were once common forms of early American “soft drinks” (similar to modern Scandinavian saft). Made of fruit mixed with vinegar and sugar, which was then semi-fermented and added to water as a flavoring, raspberry shrub was among the most popular.
This recipe is taken verbatim from “The American Frugal Housewife” by Mrs. Child, which was originally published in 1833.
Raspberry shrub mixed with water is a pure, delicious drink for summer; and in a country where raspberries are abundant, it is good economy to make it answer instead of Port and Catalonia wine. Put raspberries in a pan and scarcely cover them with strong vinegar. Add a pint of sugar to each pint of juice; (of this you can judge by trying your pan to see how much it holds;) scald it, skim it, and bottle it when cold.
Mrs. Child’s recipe may leave something to be desired for modern cooks, so here is a recipe from cooks.com with more modern instructions.
You could easily substitute blackberries, blackcaps (black raspberries), marionberries, etc. for raspberries in this recipe.
Vinegar-water drinks were common in Early America as thirst-quenchers. So raspberry shrub makes a nice alternative to all those powdered “flavored water” drinks.