The series equals total balances maintained plus currency in circulation.
Board of Governors of the Federal Reserve System (US), Monetary Base; Total [BOGMBASE], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/BOGMBASE, February 27, 2020.
Release: H.6 Money Stock Measures
M1 includes funds that are readily accessible for spending. M1 consists of: (1) currency outside the U.S. Treasury, Federal Reserve Banks, and the vaults of depository institutions; (2) traveler's checks of nonbank issuers; (3) demand deposits; and (4) other checkable deposits (OCDs), which consist primarily of negotiable order of withdrawal (NOW) accounts at depository institutions and credit union share draft accounts.
Board of Governors of the Federal Reserve System (US), M1 Money Stock [WM1NS], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/WM1NS, February 27, 2020.