The 1755 Lisbon earthquake and tsunami, which killed more than a third of the capital's population and devastated the Algarve as well, had a profound effect on domestic politics and on European philosophical thought. From 1801, the country was occupied during the Napoleonic Wars. The Portuguese Court fled to Brazil. Shortly after, Brazil proclaimed its independence, under the rule of the Portuguese King Pedro IV (Emperor Pedro I of Brazil), who abdicated from the Portuguese Crown and left his daughter D. Maria I as Queen in a liberal regime.

Portuguese 19th Century is marked by the Liberalism. The divisions between king Pedro IV - liberal - and his brother, King Miguel, a conservative who overthroned Queen Maria I, led to the civil war between 1832 and 1834 and the signing of the new constitutions in 1836. The political and social evolution in the late 19th century is marked by instability.