Vault of the Ages
Poul AndersonThis classic from science fiction's Golden Age envisions a primitive future where only the forbidden technology of the past can save an endangered tribe from violent extinction
Five centuries into the future, America is no longer what it used to be. Many generations after the old civilization was consumed in a nuclear firestorm, the few survivors have returned to a simple, agrarian lifestyle and eschew the malevolent "magic" of science that brought about "the Doom." When the Dalesmen of the Alleghenies are threatened by the hostile Lann descending from the North, their chieftain's son, Carl, is dispatched to the blasted ruins of an ancient city to trade for metal and weapons.
However, something extraordinary awaits him in this feared and forbidden place: a time capsule from the twentieth century containing the essential scientific and technological information of a lost society. Carl knows his discovery can help rescue the Dalesmen's homes and farms....