A handsome yet austere example of Moderne architecture, the Post Office and Customs House, designed by consulting architect Hendrick P. Mass, is constructed of reinforced concrete. The walls have been left rough finished, while the water table and spandrels are smooth. Eleven bays of windows are inset in panels, with recessed spandrels between the stories. The piers between them are ornamented with vertical lines. The roof is flat.
Despite the obvious addition of some mail boxes, the interior is virtually unaltered, with copper mail boxes, quarry tile floor and wainscot, and highly varnished wood-paneled walls. At one end there is a mural painting depicting Wrangell's history, signed by Marianne Appel and Austin Mecklen and dated 1943.