In 1920, during the Japanese era, the town of A-kong-tien (阿公店; Pe̍h-ōe-jī: A-kong-tiàm) was renamed Okayama (岡山) and made the site of an airbase. Administratively Okayama Town (岡山街) covered modern day Gangshan District and Ciaotou District and was under Okayama District (岡山郡), Takao Prefecture. The town suffered heavy bombardment in World War II.
Following the Surrender of Japan and handover to the Kuomintang, the government continued to use the characters 岡山, but pronounces the term in Mandarin, hence Gangshan vs. "Okayama". The town continued to host Gangshan Air Base (Kangshan Air Base), and has a strong military veteran's presence as well.