A routing number is a 9 digit code for identifying a financial institute for the purpose of routing of checks (cheques), fund transfers, direct deposits, e-payments, online payments, etc. to the correct bank branch.
Routing numbers are also known as banking routing numbers, routing transit numbers, RTNs, ABA numbers, and sometimes SWIFT codes (although these are quite different from routing numbers as SWIFT codes are solely used for international wire transfers while routing numbers are used for domestic transfers).
Routing numbers differ for checking and savings accounts, prepaid cards, IRAs, lines of credit, and wire transfers.
Usually all banks have different routing numbers for each state in the US. You can find the routing number for Westmark in ID here.
Review / Comment on Twin Falls Pole Line Branch of Westmark