Tales of the origin of Siay was handed down from generation to generation by the spoken word of the elders of the Subanen tribe. History has it that, Datu Lihos, the earliest known leader of the Subanens, had a daughter named Sihay from whom Siay derived its name. Siay then was predominantly settled by the Subanens with a sprinkling of Muslims along the coasts of Payao.

          More than a century ago, as revealed in the book “The World in 1896”, Siay along with Culasian and Kabasalan was specifically mentioned as falling under the territorial jurisdiction and control of the Prince of Sibuguey and recognized by the Spanish authorities.

          The size and remoteness of the area naturally gave rise to local leaders who could provide cohesion, order and direction to pockets of some early communities in Siay, like Cando Subano and Lirayan Subano who became prominent in the northern part of Siay, Ismael Abdurahim in the central part along with the Abubakar Moro and Bacuag Subano, while Timuay Hula presided in the eastern part.

          The earlier part of the 19th century witnessed the migration of people from Luzon, the Visayas, and some other parts of Mindanao into Siay.

          Modern Siay used to be a barrio of Kabasalan but by virtue of Executive Order No. 223 dated December 28, 1956 signed by the late president Ramon Magsaysay from whom barangay Monching was named after, Siay became a full-pledged municipality with Maulod Puasa as the mayor. Puasa ruled until 1972 when he was killed by the dreaded Ilagas, a Christian militia group formed to counter another armed group called the Barracuda.



The Municipality of Siay before is a mere barangay under the territorial jurisdiction of Kabasalan. Hence, in 1956, in recognition of the untiring devotion, sincerity and the ceaseless efforts of Hon. Maulod Puasa, who was then a Municipal Councilor, Siay became a regular and distinct Municipality of the Province of Zamboanga Del Sur, on 28 December 1956, by virtue of Executive Order No. 223, signed by late President Ramon Magsaysay Jr.
At the start, the Municipality of Siay was composed of 34 Barangays with the total population of 31,816 based on 1975 PopCen. But the subsequent creation of the three (3) Municipality of Payao, Imelda and Diplahan, it reduces the number of barangays into Twenty-Nine (29) with the total population of 33,902 based on the latest 2007 PopCen. Presently, Siay is classified as 2nd class Municipality.

After Siay became a regular municipality, it then ruled by Hon. Maulod Puasa, for over fifteen (15) years until his untimely demise on 24 April 1972.
At this juncture, by Virtue of the Law of Succession Hon. Inocencio E. Eguia took over, and on 24 April of the same year,   he ran for Mayor  and  was  elected on the same
category. Until finally, the National Snap Election was called as clamored by the people and
revolution through people’s power prevailed and toppled the incumbent dictator President
Ferdinand E. Marcos.  On 25  February 1986,  Madam  Corazon  C.  Aquino,  succeeded the presidency and took her Oath of Office as the Revolutionary President of the Republic of the Philippines. By virtue of Memorandum Circular dated 17 April 1986 issued by Hon. Aquilino Q. Pimentel, Minister of Local Government, has designated Hon. Celerino B. Agraviador as Officer-In- Charge in the Office of the Municipal Mayor and to his Oath of office on 01 May 1986. In 1988, he ran for Mayoralty race and won the local polls until he passed away on 18 November 1991. And by Law of Succession he was succeeded by. Vice Mayor, Hon. Aniano A. Luspo, who then became a Municipal Mayor for almost seven years (7). In 1998, Hon. Arthur W. Luspo, M.D. son of Hon. Aniano A. Luspo was elected as Municipal Mayor for three (3) consecutive terms up to June 30, 2007, and in May 11, 2007 Hon. Julius T. Acosta, Sr. previously ABC president and retired AFP was elected as Municipal Mayor for Nine (9) years/three consecutive terms up to June 30, 2016.

The present set of Elective Officials headed by Mayor Jarvis M. Acosta, and Vice Mayor Gerald M. Acosta son of Hon. Julius T. Acosta, Sr. by virtue of their election to office last May 2016 is absolutely committed to spur sustainable development for the people of Siay.