Taika Reform
Mikawa is mentioned in records of the Taika Reform dated 645, as well as various Nara period chronicles, including the Kujiki, although the area has been settled since at least the Japanese Paleolithic period, as evidenced by numerous remains found by archaeologists. Early records mention a "Nishi-Mikawa no kuni" and a "Higashi-Mikawa no kuni", also known as . Although considered one administrative unit under the "Engishiki" classification system, this division (roughly based at the Yasaku River) persisted informally into the Edo period.