In 2002, when the Tohoku Shinkansen was extended to Hachinohe Station, the section between Morioka and Hachinohe of the Tohoku Main Line, then the longest line, was separated from the line and converted to the lines of Iwate Galaxy Railway Co., Ltd., and Aomori Railway Company Co., Ltd.; as a result, the Sanin Main Line became the longest railway line in Japan in terms of operation kilometers.
2002年にこれまで最長だったJR東日本東北本線のうち、盛岡～八戸間が東北新幹線八戸駅開業に伴い、IGRいわて銀河鉄道・青い森鉄道に転換されて分断されたため、山陰本線が営業キロ交通に関する日本一の一覧鉄道の路線となった。