[2] A famous freshwater spring known as Kōbōsui, named for Kūkai (also known as Kōbō-Daishi), gushes from the bottom of Saijō harbor and is visited by locals and Buddhist pilgrims alike to drink and worship.

[4] The most common narrative follows this interpretation and attributes both the name and the geographical boundaries of Saijō to the Taika Reforms of the 7th century, though this origin has been disputed for lack of concrete historical evidence.

[10][11] The Saijō area was part of ancient Iyo Province and has been inhabited at least as early as the Jōmon period, as evidenced by earthenware dated to approximately 6000 BC discovered in the Ichikura highland region.

The significant clustering of burial mounds from the later Kofun period in the highlands has led archaeologists to believe that the flat plain on which modern Saijō sits was either too cold or too close to the Seto Inland Sea for tomb construction.

At the beginning of the Kamakura period, the shogunate established the powerful Kōno clan as governors (shugo) over the entire Iyo Province, including Saijō.

However, in 1342, Ashikaga Takauji ordered the invasion of Iyo Province by the subordinate Hosokawa clan as part of a bid to consolidate the shogunate's power over all of Shikoku.

In 1670 the shogunate installed Matsudaira Yorizumi, a grandson of Tokugawa Ieyasu, whose descendants ruled for 10 generations until the Meiji Restoration.

Flood control projects for the Kamo River and land reclamation from the Seto Inland Sea began during the end of the Warring States Period and continued through the Edo Period, with major reclamation projects undertaken by the Matsudaira family as a means to increase their personal land holdings, 20000 koku of which were lost when they were reassigned to Saijō.

The town of Saijō was created with the merger of the villages of Tamatsu (玉津村), Omachi (大町村), and Kansai (神拝村) on February 11, 1925.

On April 29, 1941, Saijō merged with the villages of Iioka (飯岡村), Kanbe (神戸村), Tachibana (橘村) and the town of Himi (氷見町) and was raised to city status.

In response to the disaster, Mayor Kōtarō Itō established a Public Safety Division in 2006 and began a partnership with the Kyoto University Graduate Environmental Studies Department in 2007 to help make the city better prepared for emergencies.

The nearby Ichinokawa Mine was founded at the beginning the Edo period and was a major source of antimony until its closure due to lack of economic viability in 1957.

[16] The coastal area of Saijō forms the largest industrial zone in Shikoku, and covers a wide variety of fields, including materials, semiconductors, shipbuilding, beverages, power generation, and steel.

[17] The Saijo Plain in the center of the city, which is located downstream of the Kamo and Nakayama river systems, is known as a breadbasket, with production flowers, vegetables, and fruit trees, making it one of the leading agricultural areas in Ehime Prefecture.

[20] This museum located next to Iyo-Saijō Station houses a first-generation 0 Series Shinkansen bullet train car and a JNR Class DF50 diesel locomotive (No.

In July 2014, a new South Wing opened, featuring a Class C57 steam locomotive, a KiHa 65 express diesel multiple unit train car, a Class DE10 diesel locomotive, and one car of the former experimental Gauge Change Train capable of running on both express and Shinkansen tracks.

[21] The Saijō area is home to five Buddhist temples of the 88-temple Shikoku Pilgrimage: Yokomine-ji, Kōon-ji, Hōju-ji, Kichijō-ji, and Maegami-ji.

Located next to Saijō High School in the city's center, this museum displays biographical artifacts and sculptures by the famous sculptor and Saijō-native Ioki Itō (1918–1992).

The main shrine was built in the Meiji period after the shinbutsu bunri (the state enforced separation of Shinto and Buddhism) caused nearby Maegami-ji Temple to lose its status as headquarters for Ishizuchi worship.

Ishizuchi Shrine holds a 10-day ceremony and festival beginning on July 1 to mark the official opening of climbing season.

[23] This three-story building located in the "Citizen's Forest" on Mount Hachidō displays artifacts unearthed in the region, the oldest holdings being pottery and tools dating back to the Yayoi period.

Two Yayoi period dwellings were reconstructed on the top of Mount Hachidō and are accessible via several trails leaving from the museum.