The Organisation of Eastern Caribbean States (OECS) was established by the Treaty of Basseterre which was signed on June 18th 1981 by seven Eastern Caribbean Countries - Antigua and Barbuda, Dominica, Grenada, Montserrat, Saint Kitts and Nevis, Saint Lucia, and Saint Vincent and the Grenadines.
The Revised Treaty of Basseterre, signed on June 18th 2010, established the OECS Economic Union. The OECS is governed by the Authority (which consists of member states represented by their respective Heads of Government), and is administered by a Central Secretariat located in Saint Lucia.
Download the Revised Treaty of Basseterre
Website of the OECS