The U.S. Post Office and Customhouse in Gulfport, Mississippi is a historic post office and customhouse that was completed in 1910 under supervision of the U.S. Treasury Department, with James Knox Taylor as Supervising Architect. One of the oldest public or commercial structures in the city, it also has been known as Downtown Station and as Old Main Post Office. In 1963 a one-story extension to the rear was added.