Series Is Presented Here As Two Variables--(1)--Original Data, 1877-1941 (2)--Original Data, 1941-1964. Data Are For Daily Averages. Source: Data For 1877-1921: F.R. Macaulay, The Movements Of Interest Rates, Bonds Yields, And Stock Prices In The U.S. Since 1856, NBER, 1938, Table 27. Data For 1922-1941: Iron Age, Successive Issues.
This NBER data series m01130a appears on the NBER website in Chapter 1 at http://www.nber.org/databases/macrohistory/contents/chapter01.html.
NBER Indicator: m01130a
Release: NBER Macrohistory Database
National Bureau of Economic Research, Pig Iron Production for United States [M0130AUSM561NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M0130AUSM561NNBR, February 14, 2016.