 The city of Basilan itself was delimited only to the downtown area of present-day Isabela until P.D.840 finally abolished the city on December 11, 1975; the former city's territory, along with the municipality of Malamawi, was merged into the municipality of Isabela.The new province was represented in the Interim Batasang Pambansa as part of Region IX from 1978 to 1984.