The name Aleosan is an acronym derived from the three(3) flourishing towns of Iloilo; A is for Alimodian, LEO is for Leon and SAN for San Miguel where majority of the early Christian settlers came from. The seat of the municipal government is in barangay San Mateo.
Parliamentary bill no. 670 authored by Assemblyman Jesus P. Amparo and co-authored by assemblymen Blah T. Sinsuat, Ernesto F. Roldan and Tomas B. Baga Jr. sought to establish and create the Municipality of Aleosan in the Province of Cotabato, which was ultimately approved and signed into law Batas Pambansa bilang 206 on April 6, 1982. For purposes of ratification, Proclamation No. 2188 was signed by President Ferdinand E. Marcos on April 29, 1982. A plebiscite was conducted on May 7, 1982 which was unanimously confirmed the desire and aspiration of the people in the nineteen (19) barangays to become a distinct and regular municipality from Pikit its mother municipality.
Aleosan is within the political boundary of Cotabato Province. It is approximately sixty-five (65) kilometers from the capital town of Amas which is barely two (2) hours ride from the seat of its municipal government. It is bounded on the west by Midsayap; on the north by Libungan and on the east and south by Pikit.
Aleosan is a progressive agricultural community with barangay and feeder roads extending into the inner portions of the town. Transport of agricultural products, mainly vegetables root crops, fruits, rice and corn was made convenient which was several years ago, done in carabao slide and horse back.