Lower Agno was initially part of the Central Cordillera Forest Reserve established on February 16, 1929 through Proclamation No. 217 issued by Governor-General Henry L. Stimson, which declared 81.8% of the entire Igorot minority lands in the Cordilleras as protected area. In a 1932 amendment, several parcels of land with an aggregate area of were excluded from the forest reserve and converted into mining areas after 146 mineral claims were approved by Governor Theodore Roosevelt Jr. More areas at the resource-rich forests of the Central Cordillera in Itogon and Tuba were opened up to mining in succeeding years by President Manuel L. Quezon, including in the Itogon barrio of Talnag in 1938, in Tuba and Itogon in 1939, and in the barrios of Acupan, Antamok, Chalecno, Gumatdang and Virac in 1941.
