The Post Office picks up the golden brick tones of the adjacent Union Station and features an arcaded central portion flanked by lower one-story wings. The tiled roof, symmetrical plan, rhythmic pace of columns across the facade, and ornamental restraint create a modern interpretation of Italian Renaissance architecture. The three entrance doors are topped with elaborate ornamental designs of stylized anthemia and eagle wings, and the building concludes with scrolled brackets along the cornice line. In combination with Union Station, the building creates a splendid backdrop for the parking plaza in front of it. On the interior, the lobby is one long open space with segmental-arched transom windows along the inside wall, which illuminate the inner workings of the building. Each bay is separated by a colorful beam and capital decorated in earthtoned geometric patterns.