Source: Railroad Gazette Magazine
This NBER data series q02084a appears on the NBER website in Chapter 2 at http://www.nber.org/databases/macrohistory/contents/chapter02.html.
NBER Indicator: q02084a
Release: NBER Macrohistory Database
National Bureau of Economic Research, Miles of Railroad Track Laid On Main Lines for United States [Q0284AUSQ376NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/Q0284AUSQ376NNBR/, October 7, 2015.