Complex sentence: Cotabato was part of the representation of Mindanao and Sulu from 1916 to 1935, when it was organized as a lone district, which included South Cotabato until 1965, and the provinces of Maguindanao and Sultan Kudarat until 1972.
Split into simpler sentences: Cotabato was part of the representation of Mindanao and Sulu from 1916 to 1935, after which it was organized as a lone district. This lone district represented South Cotabato until 1965, and the provinces of Maguindanao and Sultan Kudarat until 1972.