For the purposes of introducing the novel, "The Custom-House" offers a conceit for telling the story of Hester Prynne and Arthur Dimmesdale's doomed romance. The narrator finds the embroidered letter "A" that marked Hester as an adultress; moreover, he finds a manuscript that recorded the events of the seventeenth-century drama that played out in Salem. One purpose that "The Custom-House" serves is to provide a frame for the ensuing story. It also introduces the vaguely supernatural motif of the letter's power as the narrator holds the embroidered cloth to himself and feels a burning sensation.

A second purpose that "The Custom-House" serves is to allow Nathaniel Hawthorne to critique the corruption and incompetence of the Salem custom-house. Hawthorne had served as a customs officer in Salem before losing the position for political reasons, and his time in the post enabled him to see clearly that the mostly elderly men who filled their days in nominal positions were there only because of family connections. Hawthorne had many ill feelings about the Puritan past because of his great-grandfather's involvement as a judge during the Salem witch trials, and the emptiness of his own position in the customs office informed many of the critical views of the narrator of both "The Custom-House" and The Scarlet Letter.