Westamerica Bank, St. Helena Branch Basic Info Reviews Routing Numbers Map & Direction Name: Westamerica Bank, St. Helena Branch Main Office: No Service: Full Service Brick and Mortar Office Location: 1000 Adams Street St. Helena, California 94574 Napa County View other branches Phone: 707-968-3535 Please enable JavaScript to view the comments powered by Disqus. Routing NumberProcess ACH TransferProcess Wire Transfer121137001YN121140218YY121141000YN121141615YN From: To: