The three countries agreed to establish a union with the signing of the Treaty of Amapala on 20 June 1895. On 15 September 1896, after the countries had all ratified the treaty individually, the union was formally confirmed. The republic was rechristened the "United States of Central America" when its constitution came into effect on 1 November 1898. The capital was to be located at the Honduran town of Amapala on the Gulf of Fonseca. The union was dissolved after General Tomás Regalado seized power in El Salvador on 21 November.
Before its dissolution, the Greater Republic established diplomatic relationships with the United States. Guatemala and Costa Rica both considered joining the union, but neither ultimately did.