United States Postal Service

The official postal service of the United States, it was an original cabinet department, but was later converted to a government-owned corporation. 
TIMELINE
* 1639 - Richard Fairbanks' tavern in Boston named repository for overseas mail
* 1775 - Benjamin Franklin, first Postmaster General under Continental Congress
* 1789 - Samuel Osgood, first Postmaster General under Constitution
* 1823 - Navigable waters designated post roads by Congress
* 1825 - Dead letter office
* 1829 - Postmaster General joins Cabinet
* 1830 - Office of Instructions and Mail Depredations established, later Office of the Chief Postal Inspector
* 1838 - Railroads designated post routes by Congress
* 1845 - Star routes
* 1847 - Postage stamps
* 1852 - Stamped envelopes
* 1855 - Registered Mail
* 1855 - Compulsory prepayment of postage
* 1858 - Street letter boxes
* 1860 - Pony Express
* 1862 - Railway mail service, experimental
* 1863 - Free city delivery
* 1863 - Uniform postage rates, regardless of distance
* 1863 - Domestic mail divided into three classes
* 1864 - Post offices categorized by classes
* 1864 - Railroad post offices
* 1864 - Domestic money orders
* 1869 - Foreign or international money orders
* 1872 - Congress enacts Mail Fraud Statute
* 1873 - Penny postal card
* 1874 - General Postal Union (later Universal Postal Union)
* 1879 - Domestic mail divided into four classes
* 1880 - Congress establishes title of Chief Post Office Inspector
* 1885 - Special Delivery
* 1887 - International parcel post
* 1893 - First commemorative stamps
* 1896 - Rural free delivery, experimental
* 1898 - Private postcards authorized
* 1902 - Rural free delivery, permanent
* 1911 - Postal savings system
* 1911 - Carriage of mail by airplane sanctioned between Garden City and Mineola, NY; Earle H. Ovington, first U. S. mail pilot
* 1912 - Village delivery
* 1913 - Parcel post
* 1913 - Insurance
* 1913 - Collect-on-delivery
* 1914 - Government-owned and -operated vehicle service
* 1916 - Postal Inspectors solve last known stagecoach robbery
* [[1918 - Airmail
* 1920 - Metered postage
* 1920 - First transcontinental airmail
* 1924 - Regular transcontinental airmail service
* 1925 - Special handling
* 1927 - International airmail
* 1935 - Trans-Pacific airmail
* 1939 - Trans-Atlantic airmail
* 1939 - Autogiro service, experimental
* 1941 - Highway post offices
* 1942 - V-mail
* 1943 - Postal zoning system in 124]] major post offices
* 1948 - Parcel post international air service
* 1948 - Parcel post domestic air service
* 1950 - Residential deliveries cut from two to one a day
* 1953 - Piggy-back mail service by trailers or railroad flatcars
* 1953 - Airlift
* 1955 - Certified mail
* 1957 - Citizens' Stamp Advisory Committee
* 1959 - Missile mail dispatched from submarine to mainland Florida
* 1960 - Facsimile mail
* 1963 - ZIP Code and sectional center plan
* 1964 - Self-service post offices
* 1964 - Simplified postmark
* 1965 - Optical scanner (ZIP Code reader tested)
* 1966 - Postal savings system terminated
* 1967 - Mandatory presorting by ZIP Code for second - and third-class mailers
* 1968 - Priority Mail, a subclass of First-Class Mail
* 1969 - Patronage no longer a factor in postmaster and rural carrier appointments
* 1969 - First die proof of a postage stamp canceled on moon by Apollo 11]] mission
* 1970 - MAILGRAM
* 1970 - Postal Reorganization Act
* 1970 - Express Mail, experimental
* 1971 - United States Postal Service began operation; Postmaster General no longer in Cabinet
* 1971 - Labor contract achieved through collective bargaining for the first time in history of federal government
* 1971 - Star routes changed to highway contract routes
* 1971 - National service standards established: overnight delivery of 95% of airmail within 600]] miles and 95% of First-Class Mail within local areas
* 1972 - Stamps by mail
* 1972 - Passport applications accepted in post offices
* 1973 - National service standards expanded to include second-day delivery of parcel post traveling up to 150]] miles, with one-day delivery time added for each additional 400]] miles
* 1974 - Highway post offices terminated
* 1974 - First satellite transmission of MAILGRAMs
* 1976 - Post office class categories eliminated
* 1976 - Discount for presorted First-Class Mail
* 1977 - Airmail abolished as a separate rate category
* 1977 - Express Mail, permanent new class of service
* 1977 - Final run of railroad post office on June 30
* 1978 - Discount for presorted second-class mail
* 1978 - Postage stamps and other philatelic items copyrighted
* 1979 - Discount for presorted bulk third-class mail
* 1979 - Postal Career Executive Service (PCES)
* 1980 - New standards require envelopes and postcards to be at least 3]] 1/2" high and 5" long to be mailable
* 1980 - INTELPOST (high-speed international electronic message service)
* 1981 - Controlled circulation classification discontinued
* 1981 - Discount for First-Class Mail presorted to carrier routes
* 1982 - Automation begins with installation of optical character readers
* 1982 - E-COM (Electronic Computer-Originated Mail, electronic message service with hard copy delivery)
* 1983 - ZIP + 4
* 1983 - Ended public service subsidy from federal government
* 1984 - Integrated retail terminals automate postal windows
* 1985 - Jackie Strange, first female Deputy Postmaster General
* 1985 - E-COM terminated
* 1986 - International Priority Airmail
* 1986 - Postal Service realigned; field divisions created
* 1987 - Small parcel and bundle sorters
* 1987 - Stamps by phone
* 1987 - Multiline optical character readers ordered
* 1988 - Inspector General's Act extends duties of Chief Postal Inspector
* 1989 - Universal Postal Union Congress in Washington, DC
* 1990 - Wide area barcode readers
* 1990 - Easy Stamp, allowing purchase of stamps through computers
* 1990 - International business reply service
* 1991 - Independent measurement of First-Class Mail service
* 1992 - Remote barcoding system
* 1992 - Reorganization: regions, divisions and management sectional centers replaced by area and district offices for customer service and mail processing
* 1992 - Stamps sold through automatic teller machines
Source: http://www.usps.gov/history