The Organisation of Eastern Caribbean States (OECS) came into being on 18 June 1981, when seven Eastern Caribbean countries signed a treaty agreeing to cooperate with each other and promote unity and solidarity among the Members. The Treaty became known as the Treaty of Basseterre, so named in honour of the capital city of St. Kitts and Nevis where it was signed.

Following the collapse of the West Indies Federation, and prior to the signing of the Treaty of Basseterre, two caretaker bodies were created: the West Indies Associated States Council of Ministers (WISA) in 1966 and the Eastern Caribbean Common Market (ECCM) in 1968.

As the islands gained their independence from Britain it became evident that there was need for a more formal arrangement to assist with their development efforts. So it was that the OECS was established. The WISA Secretariat became the central secretariat of the OECS and the ECCM, the Economic Affairs Secretariat.

In mid 1997, as a result of restructuring of the organisation, the Economic Affairs Secretariat was merged into and became a Division of the OECS Secretariat in St Lucia. The OECS is now a nine member grouping comprising Antigua and Barbuda, Commonwealth of Dominica, Grenada, Montserrat, St Kitts and Nevis, St Lucia and St Vincent and the Grenadines. Anguilla and the British Virgin Islands are associate members of the OECS.

Signatories to the Treaty of Basseterre 18 June 1981
Front row (l-r): DPM Lester Bird of Antigua and Barbuda, PM Eugenia Charles of Dominica, Foreign Minister Hudson Tannis of St. Vincent and the Grenadines, PM Kennedy Simons of St. Kitts and Nevis (fifth from left), PM Winston Cenac of Saint Lucia (sixth from left), PM Maurice Bishop of Grenada (extreme right) and back row: second from left Franklyn Margetson of Montserrat. Others include back row, extreme right, Foreign Minister Peter Josie, of Saint Lucia and front row fourth from left Augustus Compton Executive Secretary of the WISA Council

The OECS is administered by a Central Secretariat located on Morne Fortune, Castries, Saint Lucia. The Secretariat is headed by the Director General who is responsible to the Authority. Over the years several subsidiary and autonomous institutions have been created.

The OECS Authority – the highest decision making body of the OECS comprising the collective of the OECS Heads of Government which meets twice a year

The Economic Affairs Council – which is essential responsible for driving the creation and operationalization of the economic union

Councils of Ministers – include Ministers of Health, Ministers of Social & Human Development, Ministers of Education, Ministers of Trade, and Ministers of Foreign Affairs.

OECS Assembly – a unique Parliament of the OECS in which each member state sits – not as Government and Opposition – but as a national delegation to debate and discuss matters relevant to the perfection of the union.

The OECS Commission – the administrative arm of the OECS responsible for supporting and facilitating the work of the organs of OECS integration.

The Islands share a single currency, the Eastern Caribbean Dollar ($2.70 ECD = 1 USD). The operation of the currency is overseen by the Eastern Caribbean Central Bank, the monetary authority for the seven OECS governments and the government of Anguilla (The British Virgin Islands uses the US Dollar as their de facto currency).

The Islands also share a common Supreme Court: The Eastern Caribbean Supreme Court, with its two divisions, the High Court and the Court of Appeal. The Supreme Court is headed by the Chief Justice. High Court judges are based in each Member State, but the judges of the Court of Appeal are resident in Saint Lucia and travel to each territory to hear appeals from the High Court. Final appeals go to the Privy Council in the UK.

The Revised Treaty was signed on June 18th, 2010 in St. Lucia, during the 51 Meeting of the Authority of Heads of Government of OECS Member States.

The Treaty establishes the OECS economic union, making possible the creation of a single financial and economic space within which goods, people and capital move freely, monetary and fiscal policies are harmonized and countries continue to adopt a common approach to trade, health, education and environment, as well as to the development of such critical sectors as agriculture, tourism and energy.

Significantly, the Treaty paves the way for the introduction of legislative competence at the regional level, so that Member States of the Organisation act in concert to develop and enact legislation in certain areas specified in the Treaty.