From the bottom of sea to the plateau!
The Koumi Line runs along the highest altitude of any JR Line. However, Sakudaira, where the Koumi Line runs through, was at the bottom of the sea for a long time. 30 million years ago neither the name of Sakudaira nor any human beings were living, and this why shell fossils are often found in and around this area. After that, it was raised to form a plateau due to crustal deformation, and the current topography was created about 3 million years ago, and some time after that humans settled in this land and began living there approximately 15,000 years ago. Things have changed since then!
There is no ocean but it called Koumi (Small Ocean).
By the way, why is the Koumi (Small sea) Line named this way, though it has been land for such a long time? Also, why are there place names such as Umijiri and Uminokuchi? That was because of Mt. Yatsugatake in 1100. At that time, a water vapor explosion from Mt. Yatsugatake occured, and the collapsed earth and sand blocked the Chikuma River, creating several lakes (inland seas). Among them, the small sea was named “Koumi”, and both ends of the large sea were named “Umi Nokuchi” and “Umijiri”, and the place name remained after the water withdrew. In this area, where there is no sea, the lake was called “the sea”, but it would have been surprising to see people at the time seeing the real sea. How about enjoying the view from the window of the Koumi Line while feeling such an old romance in the days when it was at the bottom of the sea and there was a small sea?
Starts from Saku line
The JR Koumi Line, which connects Shinshu Komoro and Koshu Kobuchizawa, has been loved as a plateau railway because of the magnificent appearance of the Yatsugatake range and the peaceful scenery of Nobeyama. The predecessor of the Koumi Line, Saku Railway (Komoro-Nakagome), gathered the wealth of the Saku region wealthy and bankers and put their efforts into opening that line. With the opening of the railway, the area around Nakagomi Station (Saku City) was built with new inns and shops. The Saku Railway, which started smoothly, would be extended from Komoro to Koumi by 1920 (Taisho 8th year). Eventually, there was a grand plan to connect Shizuoka Prefecture and Niigata to become the Honshu Railway, but unfortunately it was not realized.
Line length 78.9km
The Saku Railway was in a difficult situation, due to the economic recession and the appearance of regular buses. In 1945, it was acquired by the government and reborn as the Koumi Kita Line of the National Railways. On the other hand, JNR opened the Koumi Minami Line between Kobuchizawa and Kiyosato in 1958, the year before the acquisition of the Saku Railway, and construction was proceeding toward the opening of the entire line from both the Shinshu side and the Koshu side. Two years later, on November 29, 1945, Shinshu Kawakami-Kiyosato was opened, and 78.9km between Komoro and Kobuchizawa was connected by a single rail. With all this, SL's C56 steam locomotive was introduced, improving transportation capacity. After that, the baton was passed from C56 to a diesel train, and its appearance going along the track changed things a lot. In 1987, advanced efforts were made such as the introduction of the hybrid vehicle E200 series in Japan for the first time and in 2007 in the management of JR East was privatized from the National Railways. On November 29, 2015, the Koumi Line was 80 years old.