The American Pig Iron Association Discontinued Its Statistical Activites After 1926, Many Plants Closed Down And It Was Difficult To Collect Dependable Statistics. Source: The Record Book Of Business Statistics, Part 2, P. 19
This NBER data series m05016 appears on the NBER website in Chapter 5 at http://www.nber.org/databases/macrohistory/contents/chapter05.html.
NBER Indicator: m05016
Release: NBER Macrohistory Database
National Bureau of Economic Research, Merchant Pig Iron Stocks At Merchant Furnaces for United States [M05016USM576NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M05016USM576NNBR/, July 30, 2015.