How does he justify writing "the custom house "? What do you think his real purpose is?

The Custom House is largely an autobiographical sketch describing Hawthorne's life as an administrator of the Salem Custom House. It was written to enlarge the tale of The Scarlet Letter, since Hawthorne deemed the story too short to print by itself. It also serves as an excellent essay on society during Hawthorne's times, and it allows Hawthorne to add an imaginative literary device, the romantic pretense of having discovered the manuscript of The Scarlet Letter in the Custom House.