Data Are Adjusted For Economic Drift. Source: F.R. Macaulay, The Movement Of Interest Rates, Bond Yields, And Stock Prices In The United States Since 1856 (NBER, 1938), Appendix Table 10, Pp. A142-A161.
This NBER data series m13019 appears on the NBER website in Chapter 13 at http://www.nber.org/databases/macrohistory/contents/chapter13.html.
NBER Indicator: m13019
Release: NBER Macrohistory Database
National Bureau of Economic Research, American Railroad Bond Yields, High Grade for United States [M13019USM156NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M13019USM156NNBR, February 13, 2016.