First Interstate Bancorp traces its intricate corporate lineage back to its roots as Western Bancorporation, a massive multi-state bank holding company originally created as an affiliate of Transamerica Corporation before being spun off as an independent corporate entity. Operating a vast network of affiliate banks across numerous western states, the holding company decided to unify its disparate regional operations under a single, cohesive brand identity. In the early 1980s, corporate leadership officially rebranded the holding company and its associated banking subsidiaries as First Interstate Bank, establishing a powerful regional presence that later became the target of historic high-profile takeover battles in the American banking sector.