The hypothesis proposed by Nakamura (1983) that the North-Eastern Japan is a part of the North-American Plate has been re-examined from geological and geomorphological veiw points. One of the difficulties is that active faults are not found along the entire length of the Itoigawa-Shizuoka Tectonic Line which is considered as the boundary between rigid plates. The beginning of the convergence at the Itoigawa-Shizuoka Tectonic Line is much older than the age speculated by SENO (1987). An alternative hypothesis that the Itoigawa-Shizuoka Tectonic Line is a moribund plate boundary is proposed.