Oigamori is the area where a road called Nagasawa-Kobuchisawa Line that existed since olden times (now a prefectural road leading to Kobuchisawa-cho Town from Nagasawa Intersection on National Route 141) intersects with the Middle Bomichi Road. Since the Middle Ages, it was a strategic spot where traffic passed through to go toward the Suwa region from Koshu.
There are records indicating that Takeda Harunobu (Shingen) passed through Oigamori Bansho Guard Station in 1542 when he conquered the Suwa Basin and embarked on an invasion of Shinano.
In the Edo Period (1603–1868), Oigamori Bansho was replaced with a smaller gated checkpoint called kuchidome-bansho.