PINE ISLAND, MN 55963. Pine Island Bank's routing number (the leftmost number on the bottom of a check) is 91903967. Sometimes, banks have multiple routing numbers for different branches or uses. Please make sure this is the correct routing number for your branch! The main phone number for Pine Island Bank is 507-356-6662. The assigned Federal Reserve Office for Pine Island Bank is Fed 091000080. what is a bank routing number? A bank's Routing Transit Number (RTN) is a 9-digit code used to identify your bank on checks, direct deposit, bill pay, and in other transactions.