The Jones Law of 1916 restructured the Philippine Legislature into the Senate (which replaced the Philippine Commission) and the House of Representatives (which replaced the Philippine Assembly). The Philippines was thus divided into 12 senatorial districts, which were to be represented by two senators each: the first placer in each senatorial district would serve for six years, while the second placer would serve for three years. Every three years thereafter, one senator for each district was elected to serve for six years. All of the senators were elected by their senatorial district except the senators of the non-Christian Twelfth District, who were appointed by the Governor-General.
 Clarita R. Carlos and Rommel C. Banlaoi, Elections in the Philippines: From Pre-colonial Period to the Present (Makati City: Konrad Adenauer Foundation, 1996), p. 30.