HAO788 Bank of the West officially became part of BMO in 2023, following BMO's $16.3 billion acquisition of the bank, and by mid-2023 every Bank of the West account, branch, and processing system had been fully converted over to BMO's platform. If you're searching for a Bank of the West routing number today, it's likely because you still have an old check, a saved payment profile, or paperwork listing the bank's name and need to know whether that number still works — or what to use instead. The short answer is that your account itself hasn't disappeared, but the routing number tied to it may have changed depending on when and how your account was migrated.

Before the merger, Bank of the West operated with 18 distinct routing numbers spread across its footprint in California, Texas, Iowa, New Mexico, and Oregon, with the vast majority of accounts — including the widely used 121100782 — tied to its Los Angeles processing center. These legacy numbers were built around the bank's original regional structure and, for a transition period, many continued to route deposits correctly as BMO integrated its systems. However, relying on a legacy number indefinitely is risky, since BMO has been steadily consolidating processing under its own set of routing numbers, and using an outdated code can cause a deposit or transfer to be delayed or rejected.

The safest way to confirm your current routing number is to check a recent BMO statement or check, log into BMO's online banking or mobile app, or call BMO customer service directly and reference your former Bank of the West account. Avoid relying solely on old paperwork, saved routing numbers in payment apps, or third-party lists — including this one — for anything time-sensitive like a large wire transfer, and instead treat those as a starting point to verify rather than a final answer. Taking a few minutes to confirm the number directly with BMO is the best way to make sure your direct deposit, bill payment, or transfer lands in the right place without unnecessary delays.