In early 1924, a group of Ilocano settlers with a number of Kapampangans and Pangasinenses from Tarlac arrived in Casiguran, which was then part of Nueva Vizcaya.

[6][7] Finding the natives unfriendly to them, the settlers moved along the coastline going north and settled finally to what is now called Dilasag.

It was declared a sitio of barangay Culat and eventually a barrio of Casiguran in consideration of its rapid progress and development.

In 1959, Quezon 1st District Representative Manuel Enverga introduced House Bill No.

2452 on June 21, 1959, making Dilasag a municipal district and separating it from Casiguran.