Innai Oil Field was once one of the largest oil-producing fields in Japan.
An oil mining company began exploratory drilling in 1922, leading to rapid development of the area. Of the four oil fields nearby (Innai, Katsurazaka, Kotaki, and Kamihama), Innai had the largest production rate.
In 1935, oil production reached its peak at 113,000 m3 per year, but it gradually decreased, and the oil field closed in 1995.
Today, the remains of the equipment left at the site offer a glimpse into the past.