Yamakami Castle was constructed by Goro Takatsuna, the grandson of Fujiwara
Hidesato. Takatsuna's son, Takamitsu, was a supporter of Minamoto no Yoritomo.
His descendants continued to rule the area. During the reign of Lord Uesugi,
the family became very prominent in the eastern part of Joshu (former name
for Gunma Prefecture). However, the military supporters of Lords Hojo,
Takeda and Uesugi were disbanded during the period of Warring States and
the castle was abandoned by the end of the 16th century.
The castle was constructed in a linked formation, with the buildings in a line. From the north was the Sasakaku (sasa enclosure) followed by the Kitakaku (north enclosure), Honmaru (main enclosure), Ni-no-maru (second enclosure), San-no-maru (third enclosure), and Nankaku (south enclosure). The ruins of a lookout post can be seen in the south enclosure.
The castle is 650 meters in length from north to south, and 220 meters
from east to west, making it a long narrow construction. Unlike the usual
enclosure construction style, the castle had high enclosures, for which
it is sometimes called a hill castle. The surrounding valley and Warabisawa
River provide natural protection for the castle. "Joka machi"
(castle town) names still exist in the area, such as "Moto machi"