What purpose does "The Custom House" serve?

The Custom House serves the small ship traffic going through the port, but it is usually a quiet place requiring only minimal work.

Much of the story deals with long descriptions of the various men with whom he worked in the Custom House. General Miller, the Collector, is the oldest inhabitant, a man who maintained a stellar career in the military but who has chosen to work in the Custom House for the remainder of his years. As for the Inspector, his job was created by the man's father decades earlier, and he has held the position ever since. The Inspector is the most light-hearted of the workers, constantly laughing and talking in spite of his age.

The upstairs of the Custom House was designed to accommodate a large movement of goods through the port, and it is in ill repair since it soon became extraneous. Hawthorne says that the large upstairs hall was used to store documents, and it is here that he has found an unusual package. The package contains some fabric with a faded letter A imprinted on the cloth, with some papers describing the entire story behind the letter. This is the story that Hawthorne claims is the basis for The Scarlet Letter.