When the place improved and its population grew to no less than 5,000 people, it became a town through a petition filed by the inhabitants through the initiative of two early leaders, Kabesang Prudencio Esquivel and Kapitan Antonio Embuscado.

The Spanish officials signed the papers granting the petition that "Ibayong Ilog" be a town in Factoria (now San Isidro) which was then the capital of Nueva Ecija.

The declaration was brought to Governor-General Juan de Lara e Irigoyen in Manila, and afterwards was submitted to the Vice-General of the Philippines in the person of Rev Gregorio Martínez.

Father Martínez marked the document as approved but later wrote in his own wish that the name "Ibayong Ilog" be changed to the name of his birthplace of Jaén, Spain.

On August 24, 1896, its people revolted against the Spaniards and in September of the same year, armed with bolos and spears, ambushed and killed forty Spanish soldiers in Lumanas (now a Sitio of Barangay Santo Tomas South).

Distilled and purified water processors, mobile phone card dealers, cable and landline telephone businesses are also present in the municipality.

Most of the unemployed and out-of-school youths are given manual labor by private contractors and the local government unit, such as construction workers and street sweepers.