The original town of Dupax is the largest municipality of the province of Nueva Vizcaya in terms of land area. But in 1971, the Congress passed into law Republic Act 6372 otherwise known as ""An Act Creating the Municipality of Dupax del Sur from the Municipality of Dupax in the province of Nueva Vizcaya"", sponsored by Congressman Benjamin B. Perez in the Philippine House of Representatives and Senator Leonardo B. Perez in the Philippine Senate. president Ferdinand Marcos amended some sections and signed it into law with the promulgation of Presidential Decree 586 on November 26, 1974 which paved the way for the division of Dupax into two municipalities: Dupax del Norte and Dupax del Sur.