Post Offices brace for busiest day of the year Posted on December 16, 2014 by Chicago 1 Chicago Chicago News & Search 1 News - 1 eMovies - 1 eMusic - 1 eBooks - 1 Search Search for: The U.S. Postal Service says that Monday marks its busiest mailing day of the year, with more than 640 million cards, letters and packages expected to be processed, including the facility at 433 W. Harrison. | Richard A. Chapman/Sun-Times Media 1 Chicago Chicago News & Search 1 News - 1 eMovies - 1 eMusic - 1 eBooks - 1 Search Search for: