The first steps in the cooperation between Estonia, Lithuania, and Latvia were made in the 1920s and 30s, soon after the three states achieved independence. The cooperation among the Baltic nations became especially visible in the end of the 1980s and beginning of the 1990s in the fight to restore national independence. In that way, the Baltic Chain, which took place on 23 August 1989 and whose 25th anniversary will be celebrated in 2014, gained large amounts of attention in the world.
Full-scale co-operation among Estonia, Latvia and Lithuania was re-established on 12 May 1990 when the Declaration on Unity and Co-operation by the Republic of Estonia, Republic of Latvia and Republic of Lithuania was signed in the White Hall of the Riigikogu in Tallinn. That decision was in line with the Treaty on Concord and Co-operation concluded between the three Baltic states in 1934 in Geneva.
After the restoration of independence, structures for intergovernmental and interparliamentary cooperation were quickly built up. In 1994, a whole series of foundational documents were approved. Since 2004, activity in NATO and the European Union have become important areas of cooperation. In the same period, some changes were also made to make it more up-to-date.