Source: Board of Governors of the Federal Reserve System (US)  

Release: H.3 Aggregate Reserves of Depository Institutions and the Monetary Base  

Units:  Billions of Dollars, Seasonally Adjusted

Frequency:  Monthly

This series has been discontinued. As of July 11, 2013 data in the new H.3 statistical release are no longer adjusted for regulatory changes in reserve requirements and are no longer seasonally adjusted. You can access not seasonally adjusted series of total reserves at https://fred.stlouisfed.org/series/TOTRESNS.