The Hukou San-Yuan Temple is the center of faith in the old Hukou area. The basic layout includes Sanchuan Hall, corridors, left and right protector halls, central courtyard, main hall, and left and right ear houses. The temple follows a unique pattern of single-protector dragon courtyard. Next to the temple is the famous Hukou old street, which is one of the major tourist attractions in this county. The temple enshrines the Three Officials, Mazu, Guanyin, and other deities. In 2001, it was designated as a county-level historic site.
The Hukou area was gradually settled by Hakka immigrants during the Qianlong and Jiaqing periods of the Qing dynasty. Old Hukou, situated between the mountains and the platform, became a community center and a hub for goods.
The construction of the railway from Keelung to Hsinchu began in 1887 (13th year of Guangxu), with a station set up in old Hukou. The railway was completed in 1895 (19th year of Guangxu), bringing business opportunities to old Hukou. The commercial town flourished rapidly, becoming a major commercial center.
The San-Yuan Temple was designated as a county-level historic site by the county government in 2001. However, during the 921 earthquake, the historic site suffered severe damage, including cracked walls and leaky roof tiles.
The temple's restoration project was undertaken by the Xu Yujian Architect Office. The project was tendered in December 2002, and construction began in February 2003 and was completed in May 2005. The restoration was fully funded by the 921 Community Reconstruction and Revitalization Foundation, approved by the Ministry of the Interior.