Following its independence from Portugal in 1822, Brazil was confronted by unrest in the Banda Oriental. On April 19, 1825, a group of Uruguayan revolutionaries (the famous Thirty-Three Heroes) led by Juan Antonio Lavalleja, reinforced by Argentine troops, crossed the Río ÍÍÍÍde la Plata from Buenos Aires and organized an insurrection that succeeded in gaining control over the countryside. On August 25, 1825, in a town in the liberated area, representatives from the Banda Oriental declared the territory's independence from Brazil and its incorporation into the United Provinces of Río de la Plata. Brazil declared war on them. The ensuing conflict lasted from December 1825 to August 1828.

In 1828 Lord John Ponsonby, envoy of the British Foreign Office, proposed making the Banda Oriental an independent state. Britain was anxious to create a buffer state between Argentina and Brazil to ensure its trade interests in the region. With British mediation, Brazil and Argentina signed the Treaty of Montevideo at Rio de Janeiro on August 27, 1828, whereby Argentina and Brazil renounced their claims to the territories that would become integral parts of the newly independent state on October 3. However, Argentina and Brazil retained the right to intervene in the event of a civil war and to approve the constitution of the new nation.

Argentine and Brazilian troops began their withdrawal, while a constituent assembly drew up the constitution of the new country, created its flag and coat of arms, and enacted legislation. The constitution was approved officially on July 18, 1830, after having been ratified by Argentina and Brazil. It established a representative unitary republic--the República Oriental del Uruguay (Oriental Republic of Uruguay), the word oriental (eastern) representing the legacy of the original designation of the territory as the Banda Oriental. The constitution restricted voting, made Roman Catholicism the official religion, and divided the territory into nine administrative jurisdictions known as departments (see Constitutional Background , ch. 4).

Data as of December 1990