Prentice Alvin

Prentice Alvin (1989) is an alternate history/fantasy book that was written by Orson Scott Card. It is the third book in Card's "The Tales of Alvin Maker" series and is about Alvin Miller, the seventh son of a seventh son (this gives him magical powers). "Prentice Alvin" was considered for the Nebula Award for Best Novel in 1989 and the Hugo Award for Best Novel in 1990.
Plot summary.
After being released from his time with Ta-Kumsaw, an Indian leader who taught Alvin the ways of Indian people, he sets out to start his apprenticeship as a Smith in the town where he was born.
While there he meets a young half-black boy by the name of Arthur Stuart, the son of a slave and a slave-owner who has been taken in by the owners of the town's guesthouse.
Another new friend comes in the form of Miss Peggy Larner, who he later finds out that she is the "torch" who helped him to be born so many years ago, and with whom he has been linked to since that day.
Eventually, Alvin is forced into helping Arthur to escape from some slave-hunters, which requires him to change Arthur's DNA to prevent the hunters' knacks (powers) from finging him. Alvin also creates a plow of living gold, which is bestowed with magic, as his journeyman work to release himself from his apprenticeship as a Smith (and also as a Maker).
The story ends with Alvin and Arthur leaving the town and going back to Alvin's home in the west.