Irong-Irong

Irong-Irong developed at the mouth of the river that gave Iloilo its later name. Its winding navigable channel, the narrow Iloilo Strait and the shelter of Guimaras made a useful harbour for vessels of moderate size. Spanish authority had earlier centred on nearby Arevalo, but attacks on that coastal settlement encouraged a shift toward the protected river mouth. Dutch assaults in 1609, 1614 and 1616 formed part of this struggle for the Panay coast.

In 1617 the Spanish built the Fort of Our Lady of the Rosary, later called Fort San Pedro, to defend the port. Its stone-and-mortar walls formed a square with four bastions. The fortified harbour became a gathering point for Panay's agricultural and manufactured goods, with rice among the products sought by ships from elsewhere in the Philippine archipelago.