For checks to work, banks need to cooperate in interstate check clearing houses, which brings them well within "interstate commerce". This is one of many exampl

For checks to work, banks need to cooperate in interstate check clearing houses, which brings them well within "interstate commerce". This is one of many examples. But, IIRC, you can set up a bank absent checking services, wires, FDIC protection, etc. and operate entirely within one state. Good luck attracting customers.