Among the most memorable event in the chronicle of Saguday is June 21, 1959, the founding of this town as a regular municipality of then Province of Nueva Vizcaya by virtue of House Bill No. 2541, authored by Leonardo B. Perez, then Congressman of the Lone District of Nueva Vizcaya which pursuant to the provisions of Article VI, Section 20 (1) of the Philippine Constitution, became a law without the signature of President Carlos P. Garcia, entitled Republic Act No. 2519. Pursuant to Section 1 of this law, the seven barrios composing the Municipality of Saguday are as follows: La Paz, Saguday (now Rizal and Magsaysay), Salvacion, Sto. Tomas which were separated from the Municipality of Diffun; while Dibul, Mangandingay and Tres Reyes were separated from the Municipality of Aglipay.

Originally, Saguday was a barrio of the Municipality of Santiago, Isabela, however, upon the final settlement of the boundary dispute between Isabela and Nueva Vizcaya, Saguday became a regular barrio of Diffun by virtue of an Executive Order No. 386, issued by then President Elpidio Quirino.

The naming of Saguday has no legendary story or folktale. It was named by Mr. Jose Cardenas of San Jose, Nueva Ecija, the grandfather of former Mayor Leandro G. Cardenas who came to visit his kins in Saguday. The word Saguday is an Ilocano term which connotes that one possesses good traits and blessed with clean mind, heart and soul.

The first settlers of Saguday were spearheaded by the adventurous and hardworking Ilocanos composed of the families of Corpuz, Cortez, Cabiles, Guzman and Bacani who hailed from the Province of Pangasinan, the Pagbilao and Olonan family from Ilocos Region, and the families of Cardenas, and Tomas from the Province of Nueva Ecija, who all came to exploit the vast virgin lands and forest of this very promising valley.

In August 16, 1959, the founding set of Local Officials to govern the Local Government Unit appointed by then President of the Republic of the Philippines Carlos P. Garcia have assumed office, with then Luis C. Lucas, Sr. as the Municipal Mayor, while the late Nicanor Pagbilao as the Municipal Vice Mayor.

Saguday was born as a sixth class municipality composing of seven (7) barrios, however, in the year 1980 and 1981, two (2) additional barangays were created. Barangay Cardenas was created in 1980 pursuant to Sangguniang Bayan Resolution No. 02, series of 1980, while Barangay Gamis was founded in 1981, pursuant to Resolution No. 05, Series of 1981. At present, Saguday is still a 5th Class Municipality due to its limited income which is attributed to scarce resources.

Upon the creation of the Municipality of Saguday, the urban core was divided into two barrios : District I now Barangay Magsaysay has been the seat of the Municipal Government from then up to present, and District II now Barangay Rizal.