Source: Federal Reserve Bank of St. Louis  

Release: St. Louis Monthly Reserves and Monetary Base  

Units:  Billions of Dollars, Not Seasonally Adjusted

Frequency:  Monthly

Updates of this series will be ceased on December 20, 2019. Interested users can construct a proxy by summing Currency in circulation (H.4.1 release); Service Related Balances and Adjustments (H.4.1 release); and Reserve Balances with FR Banks (H.4.1 release). The discontinued series plotted on the same graph with the calculated data can be accessed for comparison at https://fred.stlouisfed.org/graph/?g=oJ6w
For more details, see the FRED Announcement.