Omiya Hachimangu was founded in 1063 by Minamoto no Yoriyoshi upon his return from the Oshu campaign. His son Minamoto no Yoshiie (1039–1106), known as 'Hachimantaro Yoshiie' from his coming-of-age ceremony at Iwashimizu Hachimangu, is said to have repaired the shrine hall his father built and planted a thousand young pines in the grounds as an offering for lasting martial fortune. The era of Yoshiie's campaigns — the Later Three Years' War (1083–1087) — marked the rise of the warrior class in the late Heian period, and his grants to eastern warriors became the foundation of Minamoto prestige that endured through the Kamakura period. Yoshiie's acts of faith and patronage at this shrine firmly established it as the tutelary Hachimangu of the Minamoto clan.