[1] La Union first elected its representatives at-large during the 1898 Philippine legislative election for a seat in the Malolos Congress, the National Assembly of the First Philippine Republic, with additional seats granted to two appointed delegates.
[2] Following the installation of U.S. civil government in 1901 and the reorganization of provinces for the Philippine Assembly, La Union was divided into a first and second district.
[1] The provincewide electoral district was re-created ahead of the 1943 Philippine legislative election for a seat in the National Assembly of the Second Philippine Republic, with an additional seat assigned to its provincial governor.
The district was again utilized in the 1984 Philippine parliamentary election when La Union was granted two seats in the regular parliament.
[1][4] After 1986, La Union elected its representatives from its two single-member congressional districts restored under a new constitution.