Aizu Nishi Kaidō
The was a pre-modern highway constructed in Edo period Japan. It was built to connect Imaichi, Shimotsuke Province (in modern-day Tochigi Prefecture) with Aizuwakamatsu Castle in modern-day Fukushima Prefecture. It is roughly traced by Japan National Route 121 and Fukushima Prefectural Route 131. History and background. With the establishment of Aizu Domain, the "daimyō" Hoshina Masayuki (1611-1673) called for the construction of a road to connect his castle with the Ōshū Kaidō, which was the main route north-south from the Tokugawa shogunate's capital of Edo. Part of the reason for this  road was economic, as the Aizu area was geographically isolated by mountains. It was also political, as the "daimyō" of Aizu were required to travel back-and-forth to Edo on alternative years with a large retinue under the "sankin-kōtai" system and needed a well-maintained road with suitable post stations for rest and resupply along the route. The road Hoshina Masayuki created was marked with "ichirizuka" distance markers to facilitate travel. The road was named the or sometimes the . In addition to Aizu Domain, the route also proved popular with the "sankin-kōtai" retinues of Shibata Domain, Murakami  Domain, Shōnai Domain and Yonezawa Domain. The route was closed from 1683 to 1723, when a landslide blocked the Kinugawa River creating a natural dam. When the dam burst in 1723 during torrential rains, 1200 people were killed by the flood in downstream Utsunomiya. The road was used by the forces of the Satchō Alliance en route to destroy Aizu Domain during the Battle of Aizu in the Boshin War. In 2002, a well-preserved ten kilometer section of the route centered on Ōuchi-juku between Aizumisato and Shimogō, including Hidama Pass and Ōuchi Pass was designated a National Historic  Site of Japan. Stations of the Aizu Nishi Kaidō. The 16 post stations of the Aizu Nishi Kaidō, with their present-day municipalities listed beside them.