 Despite several of the Mountain Province's municipalities and municipal districts being annexed to the neighboring provinces of Ilocos Sur (in 1920), La Union (in 1920) and Cagayan (in 1922 and 1928), voters in these areas were still represented by the three assembly members of the Mountain Province, and two senators of the twelfth senatorial district.Only starting in 1935 were these voters extended the right to participate in electing representatives of their respective new provinces, when Act No.4203 assigned them to specific districts for the purposes of electing members of the unicameral National Assembly of the Philippines.