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, Not Seasonally Adjusted

Frequency:  Monthly

This series has been discontinued with a phase of the simplification of reserves administration (https://federalregister.gov/a/2012-8562). The simplification of reserves administration provides an opportunity to streamline the process of calculating the monetary base so that it reflects the fundamental concept of this measure. The fundamental concept of the monetary base, or "high-powered money," is the sum of total balances maintained by depository institutions at the Federal Reserve plus currency in circulation.
Please see the new monetary base at https://fred.stlouisfed.org/series/BOGMBASE.