Shield: From the Provincial Seal of Isabela where the town is located.

Rising Sun: New hope that enlightens on-going development of San Guiilermo.

Mountains: Parts of the Municipality as rolling terrain of the Sierra Madre Mountain Range.

1967: Year when Municipality of San Guillermo was created under Republic Act No. 4906.

Logs & Tree: Town's thick and virgin forest which gives additional income to the Municipality.

Corn and Banana: Major agricultural crops and biggest production for commercial purposes.

Wide Road: Road network linking remote barrios to other nearby municipalities.