Source: The Volume Of Corporate Bond Financing Since 1900 (NBER), Hickman, Pp. 326-327
This NBER data series q10074 appears on the NBER website in Chapter 10 at http://www.nber.org/databases/macrohistory/contents/chapter10.html.
NBER Indicator: q10074
Release: NBER Macrohistory Database
National Bureau of Economic Research, Bond Offerings, Par Value, Railroads for United States [Q10074USQ311NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/Q10074USQ311NNBR/, August 29, 2015.