A: Philadelphia, Pennsylvania, United States
According to Mark R. Godburn,
"the earliest known detachable paper cover issued by a publisher is on a 28-page pamphlet called Time: An Apparition of Eternity, by John William Gerar de Brahm, published in Philadelphia in 1791. The wrapping is a simple rectangular paper printed with a presentation paragraph to the reader and signed by the author. It was folded around all four sides of the pamphlet and sealed with wax.
"Many of these early detachable covers and containers can be considered precursors to dust jackets—at least with a little imagination. But it took a revolution in the way books were bound before publishers began to issue dust jackets on new books."