On September 7, 1822, Dom Pedro, the Portuguese prince left behind as regent of Brazil, drew his sword at the Ipiranga brook near Sao Paulo and declared the country independent. The words attached to the moment are "Independencia ou Morte", independence or death. He was 23. He had spent the previous year being ordered back to Lisbon by the Portuguese Cortes, which wanted to undo the elevation of Brazil to a kingdom and cut it back to a colony.
The mechanism of the split was unusual, and it explains why Brazil turned out differently from its neighbours. When Napoleon's troops occupied Portugal in 1807, the Braganza court had moved itself and the Portuguese state to Rio de Janeiro, making Brazil the seat of the monarchy for thirteen years. When John VI went home in 1821 he left Pedro behind, which left a prince with an army, a treasury and a claim to rule in place, and a Cortes in Lisbon trying to take all three away.
Pedro's support came from a coalition that wanted independence for incompatible reasons: Brazilian landowners who wanted free trade, Portuguese troops in Rio who backed him against Lisbon, and the powerful slaveholding interests of Rio de Janeiro, Sao Paulo and Minas Gerais who did not want decisions made 8,000 kilometres away. He was acclaimed constitutional emperor on October 12. He was crowned in December.
Portugal did not recognize the new country until August 1825, in a treaty negotiated under British pressure, and only after Brazil agreed to pay two million pounds in compensation and to grant Portugal favourable trading terms. Pedro I abdicated in 1831 in favour of his five-year-old son and went back to Portugal to fight his brother for the throne.
Brazil stayed one country. It stayed a monarchy for 67 years, abolished slavery in 1888, and became a republic in 1889. Those two events are connected: the monarchy lost the support of the landowners who had backed independence when it freed their slaves, and the army and the republican clubs took over a year later. September 7 is still Independence Day, the Sete de Setembro, and the site at Ipiranga has a monument and a museum.