Series Is Presented Here As Two Variables--(1)--Original Data, 1889-1915 (2)--Original Data, 1911-1939. Data Exclude Iron Ridge Area (Southern Wisconsin). Source: U.S. Bureau Of The Mines, Mineral Resources, 1914, Part 1, Pp. 496-497.
This NBER data series a01193a appears on the NBER website in Chapter 1 at http://www.nber.org/databases/macrohistory/contents/chapter01.html.
NBER Indicator: a01193a
Release: NBER Macrohistory Database
National Bureau of Economic Research, Iron Ore Production, Lake Superior Ore, Total for Lake Superior [A0193A41A418NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/A0193A41A418NNBR/, July 27, 2015.