Another view:
The Federal Reserve is Chartered by Congress just as the ill fated Fannie Mae and Freddie Mac were "chartered by congress". The rest of the previous answer is speculation.
"Economic Stability" was the mythical purpose for the creation of the Federal Reserve. The hard core facts are that the economic stability of the United States has decreased under the reign of the Federal Reserve and many noted economists believe that the policies of the Federal Reserve exacerbated and prolonged the "GREAT DEPRESSION".
The real purpose of the Federal Reserve was to give a Euorpean banking cartel control over the American Economy. The Federal Reserve Act which created this entity was passed on Christmas Eve without adequate vetting by Congress.