The Municipality of Jaen, San Isidro and San Antonio were formerly component barrios of Gapan City. Jaen then, was known as ?Ibayong Ilog?, because it is situated just across the river, which traversed the town of Gapan. Ibayong Ilog is the vernacular for ?across the river?. When San Isidro was separated from Gapan and became a town, Ibayong Ilog became one its component barrios along with San Antonio. Much later, Ibayong Ilog became a part of San Antonio when the latter was established as a Municipality separate from San Isidro.