The Metric System was invented by the French Academy of Science at the request of The National Assembly of France. Metre

Metre

The metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...

 Convention (also known as the Convention du Mètre in French, and the Treaty of the Meter in English) of May 20, 1875 is a treaty

Treaty

A treaty is an express agreement under international law entered into by actors in international law, namely sovereign states and international organizations. A treaty may also be known as an agreement, protocol, covenant, convention or exchange of letters, among other terms...

 which established three international organization

International organization

An intergovernmental organization, sometimes rendered as an international governmental organization and both abbreviated as IGO, is an organization composed primarily of sovereign states , or of other intergovernmental organizations...

s to oversee the keeping of metric standards. It was revised in 1921 by the 6th CGPM (Conférence générale des poids et mesures, or International Committee for Weights and Measures

International Committee for Weights and Measures

The Interglobal Committee for Weights and Measures is the English name of the Comité international des poids et mesures . It consists of eighteen persons from Member States of the Metre Convention...

). In 1960, the system of units it established was renamed the "International System of Units

International System of Units

The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...

" (Système international d'unités or SI).

The Convention created three main organizations, which are the General Conference on Weights and Measures

General Conference on Weights and Measures

The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures . It is one of the three organizations established to maintain the International System of Units under the terms of the Convention du Mètre of 1875...

 (Conférence générale des poids et mesures or CGPM) - a meeting every four to six years of delegates from all member states; the International Bureau of Weights and Measures

International Bureau of Weights and Measures

The International Bureau of Weights and Measures , is an international standards organisation, one of three such organisations established to maintain the International System of Units under the terms of the Metre Convention...

 (Bureau international des poids et mesures or BIPM) - an international metrology centre at Sèvres

Sèvres

Sèvres is a commune in the southwestern suburbs of Paris, France. It is located from the centre of Paris.The town is known for its porcelain manufacture, the Manufacture nationale de Sèvres, making the famous Sèvres porcelain, as well as being the location of the International Bureau of Weights...

 in France; and the International Committee for Weights and Measures

International Committee for Weights and Measures

The Interglobal Committee for Weights and Measures is the English name of the Comité international des poids et mesures . It consists of eighteen persons from Member States of the Metre Convention...

(Comité international des poids et mesures or CIPM) - an administrative committee which meets annually at the BIPM.

Countries involved

There were originally 17 countries involved with this treaty. This number grew to 21 in 1900, 32 in 1950, 44 in 1975, 48 in 1997 and 49 in 2001. Since 2005, there are 51 Member States (with year of partnership between brackets):

Germany (1875)
Argentina (1877)
Australia (1947)
Austria (1875)
Belgium (1875)
Brazil (1921)
Belarus (2003)
Bulgaria (1911)
Cameroon (1970)
Canada (1907)
Chile (1908)
The Republic of China (1977)
Caribbean Community (2005)
Antigua and Barbuda
Barbados
Belize
Cuba
Dominica
Ecuador
Estonia
Guyana
Grenada
Saint Kitts and Nevis
Santa Lucia
St. Vincent and the Grenadines
Suriname
Trinidad and Tobago
Czech Republic (1922)
North Korea (1982)
South Korea (1959)
Costa Rica (2004)
Croatia (2005)
Denmark (1875)
Dominican Republic (1954)
Egypt (1962)
Slovakia (1922)
Slovenia (2003)
Spain (1875)
United States (1878)
Philippines (2002)
Finland (1923)
France (1875)
Greece (2001)
Hong Kong (2000)
Hungary (1925)
India (1957)
Indonesia (1960)
Iran (1975)
Ireland (1925)
Israel (1985)
Italy (1875)
Jamaica (2003)
Japan (1885)
Kazakhstan (2003)
Kenya (2002)
Latvia (2001)
Lithuania (2001)
Malta (2001)
Malaysia (2001)
Mexico (1890)
New Zealand (1991)
Norway (1875)
Netherlands (1929)
Panama (2003)
Pakistan (1973)
Peru (1975)
Poland (1925)
Portugal (1876)
Romania (1884)
Russian Federation (1875)
South Africa (1964)
Sweden (1875)
Switzerland (1875)
United Kingdom (1884)
Serbia (1879)
Singapore (1994)
Thailand (1912)
Taiwan (2002)
Turkey (1875)
Ukraine (2002)
Uruguay (1908)
Venezuela (1879)
Vietnam (2003)