Although generally taken for granted, present-day postal service is of relatively recent origin. The use of postage stamps for prepayment of postage was not introduced until 1840, when the UK established a unified postage charge, the famous penny rate, to be paid by the sender of a letter regardless of the distance it had to travel. Until that year, the postal fee based on distance was often very high and was not paid by the sender but by the addressee. If the addressee could not pay, the letter was returned. Gradually, other countries introduced adhesive stamps, and their use spread to international mail. In 1863, on the initiative of the US, representatives of 15 postal administrations met in Paris to consider the problem of standardizing international postal practices.
The decisive development came with the meeting of the first international Postal Congress at Bern in 1874, at the suggestion of the German government. The Bern Congress was attended by delegates from 22 countries: 20 European countries (including Russia), Egypt, and the US. The congress adopted a treaty concerning the establishment of a General Postal Union—commonly known as the Bern Treaty—signed on 9 October 1874. This was the forerunner of the series of multilateral Universal Postal Union conventions and came into force in the following year, when the union was formally established, on 1 July 1875, to administer its operative regulations.
The 1874 Convention provided for subsequent postal congresses to revise the convention in the light of economic and technical developments. The second congress, held in Paris in 1878, changed the name of the General Postal Union to the Universal Postal Union (UPU). Four more congresses were held prior to World War I: Lisbon, 1885; Vienna, 1891; Washington, 1897; and Rome, 1906. There were five congresses between the wars: Madrid, 1920; Stockholm, 1924; London, 1929; Cairo, 1934; and Buenos Aires, 1939. The first post–World War II congress met in Paris in 1947 and arranged for the UPU to be recognized as a specialized agency of the UN family in 1948. Other congresses met at Brussels, 1952; Ottawa, 1957; Vienna, 1964; Tokyo, 1969; Lausanne, 1974; Rio de Janeiro, 1979; Hamburg, 1984; Washington, 1989; and Seoul, 1994. The 22nd congress convened in Beijing in 1999.