The marriage of Ferdinand II of Aragon and Isabella I of Castile in 1469 united the two royal lines. Madrid became the centre of political power whilst the colonisation of the Americas reduced the financial importance (at least in relative terms) of Mediterranean trade. Barcelona was a centre of Catalan separatism, including the Catalan Revolt (1640–52) against Philip IV of Spain. The great plague of 1650–1654 halved the city's population.