Although it was not issued solely for the Columbian Exposition, U.S. #E3 is considered a part of that issue. Because the then-current blue “Messenger Running” stamp (#E2) was easily confused with the 1¢ Columbian, the Columbian Exposition special delivery stamp was printed in orange. Special Delivery Service – a Revolution in Communication Special Delivery stamps were pre-payments added to the regular “lawful postage” for an extra service – immediate delivery of a letter within one mile of any special delivery post office. These special post offices were those with free routine delivery service or in larger communities with 4,000 or more people. First available in 1885, the Special Delivery service was extremely popular. At first, the service was available from 7 a.m. to midnight. The following year, the hours changed from 7 a.m. to 7 p.m. The service was so successful that in 1886, every U.S. post office began to offer Special Delivery.