Source: Federal Reserve Board, Data For 1947-1958: Supplement To Banking And Monetary Statistics, Section 1, "Banks And The Monetary System", October 1962. Data For 1959-1968: Federal Reserve Bulletin, June 1964, Pp. 686-692; August 1967, P. 1307; June 1968, P. A-92.
This NBER data series m14125b appears on the NBER website in Chapter 14 at http://www.nber.org/databases/macrohistory/contents/chapter14.html.
NBER Indicator: m14125b
Release: NBER Macrohistory Database
National Bureau of Economic Research, Currency Held By The Public for United States [M1425BUSM027NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M1425BUSM027NNBR, February 13, 2016.