Quirino Province gained its juridical status through the division of Nueva Vizcaya on June 18, 1966, under Republic Act (RA) 4734, named in honor of then-President Elpidio A. Quirino. The newly formed sub-province comprised the municipalities of Diffun, Maddela, Saguday, and Aglipay, with Hon. Jose B. Aquino serving as the first elected Lieutenant Governor in the 1967 general elections. Initially, Aglipay, Diffun, and Maddela were established on November 11, 1950, through Executive Order (EO) No. 368, with Saguday following on June 21, 1959, under RA 2519.
Three years later, on June 21, 1969, RA 5554 was passed, amending RA 4734 and establishing the municipality of Cabarroguis, carved from portions of Diffun, Saguday, and Aglipay. Former Congressmen Floro S. Crisologo and Melanio T. Singson spearheaded the enactment of this amendment.
Part of the province was formerly within Isabela but was reclaimed and reinstated into Nueva Vizcaya by the late Congressman Leon Cabarroguis, leading to the naming of the provincial capital in his honor.
Further changes came with RA 6394 on September 10, 1971, which amended RA 5554, separating Quirino from its parent province Nueva Vizcaya, establishing it as a regular province. Hon. Leonardo B. Perez, former Congressman, Senator, and Chairman of the Commission on Elections, alongside Hon. Benjamin B. Perez, former Congressman and Assemblyman for Region II, championed the passage of RA 6394 at the Interim Batasan Pambansa (IBP).
Formally established on February 10, 1972, the first set of elected provincial and municipal officials assumed office, marking the inception of the province of Quirino. Then, on February 25, 1983, Batas Pambansa Blg. 345 was enacted, dividing the municipality of Maddela and birthing Nagtipunan, the province’s youngest municipality.