| # | Image | Member | Term of office | Legislature | Party | Electoral history | Constituent LGUs |
|---|
| Start | End |
|---|
|
| District created January 9, 1907.[5][6] |
| 1 | |  | Vicente Singson Encarnacion | October 16, 1907 | October 30, 1913 | 1st | Progresista | Elected in 1907. | 1907–1912 Cabugao,Lapog,Magsingal,Santa Catalina,Santo Domingo,Sinait,Vigan |
| 2nd | Re-elected in 1909. |
| 3rd | Re-elected in 1912. Resigned on appointment ascommissioner. | 1912–1916 Bantay,Cabugao,Caoayan,Lapog,Magsingal,San Vicente,Santa Catalina,Santo Domingo,Sinait,Vigan |
| 2 | |  | Alberto Reyes | October 30, 1913 | October 16, 1916 | Progresista | Elected in 1913 to finish Encarnación's term. |
Ilocos Sur's 1st district for the House of Representatives of the Philippine Islands[edit] |
| (2) | |  | Alberto Reyes | October 16, 1916 | June 3, 1919 | 4th | Progresista | Re-elected in 1916. | 1916–1922 Bantay,Cabugao,Caoayan,Lapog,Magsingal,San Vicente,Santa Catalina,Santo Domingo,Sinait,Vigan |
| 3 | |  | Elpidio Quirino | June 3, 1919 | June 6, 1922 | 5th | Nacionalista | Elected in 1919. |
| 4 | |  | Vicente Singson Pablo | June 6, 1922 | June 2, 1925 | 6th | Demócrata | Elected in 1922. | 1922–1935 Bantay,Cabugao,Caoayan,Lapog,Magsingal,San Ildefonso,San Vicente,Santa Catalina,Santo Domingo,Sinait,Vigan |
| 5 | |  | Simeón Ramos | June 2, 1925 | June 5, 1928 | 7th | Demócrata | Elected in 1925. |
| 6 | |  | Benito T. Soliven | June 5, 1928 | June 2, 1931 | 8th | Nacionalista Consolidado | Elected in 1928. |
| 7 | |  | Pedro Singson Reyes | June 2, 1931 | September 16, 1935 | 9th | Nacionalista Consolidado | Elected in 1931. |
| 10th | Nacionalista Democrático | Re-elected in 1934. |
| # | Image | Member | Term of office | National Assembly | Party | Electoral history | Constituent LGUs |
|---|
| Start | End |
|---|
|
| (6) | |  | Benito T. Soliven | September 16, 1935 | December 30, 1941 | 1st | Nacionalista Demócrata Pro-Independencia | Elected in 1935. | 1935–1941 Bantay,Cabugao,Caoayan,Lapog,Magsingal,San Ildefonso,San Vicente,Santa Catalina,Santo Domingo,Sinait,Vigan |
| 2nd | Nacionalista | Re-elected in 1938. |
| District dissolved into the two-seatIlocos Sur's at-large district for theNational Assembly (Second Philippine Republic). |
| # | Image | Member | Term of office | Common wealth Congress | Party | Electoral history | Constituent LGUs |
|---|
| Start | End |
|---|
Ilocos Sur's 1st district for the House of Representatives of the Commonwealth of the Philippines[edit] |
| District re-created May 24, 1945. |
| 8 | |  | Jesús O. Serrano | June 11, 1945 | May 25, 1946 | 1st | Nacionalista | Elected in 1941. | 1945–1946 Bantay,Cabugao,Caoayan,Lapog,Magsingal,San Ildefonso,San Vicente,Santa Catalina,Santo Domingo,Sinait,Vigan |
| # | Image | Member | Term of office | Congress | Party | Electoral history | Constituent LGUs |
|---|
| Start | End |
|---|
|
| 9 | |  | Floro S. Crisólogo | May 25, 1946 | December 30, 1957 | 1st | Nacionalista | Elected in 1946. | 1946–1961 Bantay,Cabugao,Caoayan,Lapog,Magsingal,San Ildefonso,San Vicente,Santa Catalina,Santo Domingo,Sinait,Vigan |
| 2nd | Liberal | Re-elected in 1949. |
| 3rd | Re-elected in 1953. |
| 10 | | | Faustino B. Tobia | December 30, 1957 | December 30, 1961 | 4th | Nacionalista | Elected in 1957. |
| (9) | |  | Floro S. Crisólogo | December 30, 1961 | October 18, 1970 | 5th | Liberal | Elected in 1961. | 1961–1972 Bantay,Cabugao,Caoayan,Magsingal,San Ildefonso,San Juan,San Vicente,Santa Catalina,Santo Domingo,Sinait,Vigan |
| 6th | Nacionalista | Re-elected in 1965. |
| 7th | Re-elected in 1969. Died. |
| District dissolved into the twelve-seatRegion I's at-large district for theInterim Batasang Pambansa, followed by the two-seatIlocos Sur's at-large district for theRegular Batasang Pambansa. |
| District re-created February 2, 1987. |
| 11 | |  | Chavit Singson | June 30, 1987 | June 30, 1992 | 8th | LABAN | Elected in 1987. | 1987–present Bantay,Cabugao,Caoayan,Magsingal,San Ildefonso,San Juan,San Vicente,Santa Catalina,Santo Domingo,Sinait,Vigan |
| 12 | | | Mariano M. Tajon | June 30, 1992 | June 30, 1998 | 9th | LDP | Elected in 1992. |
| 10th | Re-elected in 1995. |
| 13 | | | Salacnib F. Baterina | June 30, 1998 | June 30, 2007 | 11th | LAMMP | Elected in 1998. |
| 12th | Lakas | Re-elected in 2001. |
| 13th | Re-elected in 2004. |
| 14 | |  | Ronald Singson | June 30, 2007 | March 7, 2011 | 14th | Lakas | Elected in 2007. |
| 15th | Nacionalista | Re-elected in 2010. Resigned after a conviction. |
| 15 | |  | Ryan Luis V. Singson | May 30, 2011 | June 30, 2013 | Biled | Elected in 2011 to finish his brother's term. |
| Nacionalista (Biled) |
| (14) | |  | Ronald Singson | June 30, 2013 | June 30, 2016 | 16th | Nacionalista | Elected in 2013. |
| 16 | | | Deogracias Victor Savellano | June 30, 2016 | June 30, 2022 | 17th | Nacionalista | Elected in 2016. |
| 18th | Re-elected in 2019. |
| (14) | |  | Ronald Singson | June 30, 2022 | Incumbent | 19th | NPC | Elected in 2022. |
| 20th | Re-elected in 2025. |