Germany was the first country to introduce a postal code system, in 1941. The United Kingdom followed in 1959 and the United States in 1963. By February 2005, 117 of the 190 member countries of the Universal Postal Union had postal code systems. A few countries that do not have national systems include Hong Kong and Panama.
Postal services have their own formats and placement rules for postal codes. In most English-speaking countries, the postal code forms the last item of the address, whereas in most continental European countries it precedes the name of the city or town. Most postal codes are numeric. The few independent nations use alphanumeric postal code systems, such as, Argentina, Canada and United Kingdom.
Before postal codes were devised large cities were often divided into postal zones or postal districts, usually numbered from 1 upwards within each city. The newer postal code systems often incorporate the old zone numbers, as with London postal district numbers, for example. Ireland still uses postal district numbers in Dublin.