Gelatin dishes as we know them date all the way back to medieval Europe. From that period up until the mid-nineteenth century, jellied dishes were foods of the elite, served as elaborate molded centerpieces on the tables of nobility. The reason was simple: the process of rendering collagen from animal bones and then clarifying it was exceptionally time-consuming, even by the slower-paced standards of the day…
Few home cooks bothered with such labor-intensive dishes—gelatin indicated to dinner guests that you had a kitchen staff large and well-appointed enough to spare the hours. This remained the case in the American colonies, where elites adapted European customs to their own tastes. Gelatin dishes were a delicacy in New York high society, where the size of one’s household staff was a status symbol; and on the plantations of the South, where enslaved cooks labored in the kitchens. At Thomas Jefferson’s estate, Monticello, wine jelly was often served to guests, Jefferson’s time in France having influenced his tastes.
—Sarah Grey, in her wonderful (and wonderfully enlightening) social history of of Jell-O salad, which ran at Serious Eats today.