The province was represented in the Interim Batasang Pambansa as part of Region IV-A from 1978 to 1984, and returned two representatives, elected at large, to the Regular Batasang Pambansa in 1984. It regained its two congressional districts under the new Constitution[2] which was proclaimed on February 11, 1987, and elected members to the restored House of Representatives starting that same year.
Municipalities: Bacnotan, Balaoan, Bangar, Luna, San Juan, San Gabriel (transferred from Mountain Province 1920; only allowed to elect representative starting 1935), Santol (transferred from Mountain Province 1920; only allowed to elect representative starting 1935), Sudipen (transferred from Mountain Province 1920; only allowed to elect representative starting 1935)
Municipalities: Agoo, Aringay, Bauang, Caba, Naguilian, Rosario, Santo Tomas, Tubao, Bagulin (transferred from Mountain Province 1920; only allowed to elect representative starting 1935), Burgos (Disdis) (transferred from Mountain Province 1920; only allowed to elect representative starting 1935), Pugo (transferred from Mountain Province 1920; only allowed to elect representative starting 1935)
^"The Malolos Congress: A Centennial publication on the inauguration of the Philippine Republic (January 23, 1899 - January 3, 1999)". National Historical Commission of the Philippines. 1999. Retrieved January 13, 2023.
^1986 Constitutional Commission (February 2, 1987). "1987 Constitution of the Philippines - Apportionment Ordinance". Retrieved June 13, 2016.{{cite web}}: CS1 maint: numeric names: authors list (link)
^Census of Population (2020). "Region I (Ilocos Region)". Total Population by Province, City, Municipality and Barangay. Philippine Statistics Authority. Retrieved 8 July 2021.
^Census of Population (2015). "Region I (Ilocos Region)". Total Population by Province, City, Municipality and Barangay. Philippine Statistics Authority. Retrieved 20 June 2016.