[1] The non-Christian areas were to be collectively represented in the upper house's 12th senatorial district by two senators, both appointed by the Governor-General.
Voters of the more Christianized provinces of Agusan, Bukidnon, Davao and Zamboanga could elect their representative through popular vote by virtue of Article VI, Section 1 of the 1935 Constitution.
[2] In the Muslim-dominated provinces of Cotabato, Lanao and Sulu, however, voter qualifications were more restrictive: the only persons allowed to vote for the province's representative were past and present municipal officials (municipal president, vice-president, municipal councilors); present senators, assembly representatives and 1935 Constitutional Convention delegates; provincial governors and members of provincial boards; and any persons currently residing in the concerned province who held any of the aforementioned positions in the past.
44 on October 13, 1936, to finally give all qualified voters of Cotabato (along with Lanao and Sulu) the right to elect their own representatives through popular vote.
[8] The present-day (North) Cotabato Province returned two representatives, elected at-large, to the Regular Batasang Pambansa in 1984.
Under the new Constitution which was proclaimed on February 11, 1987, the province was reapportioned into two congressional districts;[9] each elected its member to the restored House of Representatives starting that same year.
Despite the reallocation of 63 barangays of Cotabato to the Bangsamoro in early 2019 (later known as the Special Geographic Area or SGA), voters in that region are able to vote for local provincial positions including district representatives for the 2019 elections.