Most of land of Polanco was owned by the influential family of Realiza, led by Don Gaudencio N. Realiza during the times of American regime in the Philippines. The present land they own are large parts of Labrador (Prinda), Bethlehem, Dansullan, Guinles, Macleodes, New Sicayab, New Lebangon, Sianib, and Obay.
Polanco is politically subdivided into 30 barangays. Lingasad, Silawe, Isis, and Loboc (present-day San Miguel) became barrios in 1954.
In 1955, the sitios of Prenda, Balangbang, Marantaw, Tamsi, Serabang Gamay and Serabang Daku became barrio Prenda, while sitios of Bandera, Pian, Biga-an, Upper Genatulan, Lower Sinaman and Miasi became barrio Bandera.
In 1957, the sitios of Dilawa, Desin, Lambog, Gumatob, Boboringan, Tubongon, Debolok, Tiaman, Guintom, Lower Disoy, and New Tipan were converted into the barrio of Milad.