Source: F.R. Macaulay, The Movement Of Interest Rates, Bond Yields, And Stock Prices In The U.S. Since 1856, NBER, 1938, Table 3A.
This NBER data series m01130bb appears on the NBER website in Chapter 1 at http://www.nber.org/databases/macrohistory/contents/chapter01.html.
NBER Indicator: m01130bb
Release: NBER Macrohistory Database
National Bureau of Economic Research, Pig Iron Production for United States [M010BBUSM508NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M010BBUSM508NNBR/, August 30, 2015.