The Suffolk County National Bank of Riverhead, Sag Harbor Branch Basic Info Reviews Routing Numbers Map & Direction Name: The Suffolk County National Bank of Riverhead, Sag Harbor Branch Main Office: No Service: Full Service Brick and Mortar Office Location: 17 Main Street Sag Harbor, New York 11963 Suffolk County View other branches Phone: 631-725-3000 Please enable JavaScript to view the comments powered by Disqus. From: To: